It's because they don't have your knowledge, how are they to know how good or bad a softbox is until they've tried it? They all look like boxes with sheets in them so someone who doesn't know better will probably pump their budget into the electronics as they have a clear specification/feature set and try to save on the modifiers (or justify them as a later purchase).
I imagine you've dealt with a lot of people who fall into that category?
I can't tell if a softbox/modifier is good or bad until I have it in-hand and the ability to test it... and no, price is not always a good determinator (other than silly cheap).
OK, here's my answer, hope it helps.
Because I've already covered this, and because I'm lazy, let's start off with a copy and paste from my book "Lighting Magic"
"But, not all softboxes are equal and before I explain what you need to look for in a softbox, I’m going to bore you with some history, which I believe to be relevant.
The very first softboxes were made of sheet steel or plywood, with a ground glass screen on the front. The flash heads didn’t attach to the softboxes, they were built into them! They were extremely expensive and could only be manoeuvred into position by using a block and tackle to adjust the height! But, despite the cost and the inconvenience, just about all professional studio photographers bought them, simply because they revolutionised the quality of their work.
The next generation came out in about 1979 and had improved so much that they were unrecognisable. An American Company, Chimera, made them from fabric tent materials instead of steel, and found a way of attaching a flash head to them. The Chimera softboxes look very similar to the ones that we use today. They were a brilliant advancement and suddenly, softboxes were both affordable and easy to use.
But, they were hand-made from good quality materials and they weren’t exactly cheap. The design was then copied and re-copied, time and time again, especially in China, by factories that are not run by photographers, and they became cheaper and cheaper, using terrible materials that fall to bits, don’t control the light spill properly and with diffusers that don’t diffuse properly. These terrible copies are still available today, and they are useless.
Back then someone asked me why I chose to use very expensive Chimera softboxes instead of cheap copies. At that time I was doing a lot of fashion photography, and my answer was simple: Good softboxes make cheap clothes look expensive!
Over time though, major lighting manufacturers were able to persuade softbox manufacturers to use decent materials and improve the designs, and as a result there are now some very good ones available. Most softboxes are now made in the same factory, in a very wide range of qualities, and they are sold under a host of different brand names.
My advice to you is to first decide on the size and shape of the softbox(es) that you need, and to then decide on the design. Once you’ve done that, you can decide on the quality.
softbox size:
The larger the softbox, the softer the light, at any given distance from the subject. When you move the softbox further from the softbox the quality of the light changes. The most obvious change is to the softness of the light, because softbox size is subject to Newton’s Inverse Square Law, so if you double the distance from softbox to subject it will, in effect, only be a quarter of its original size. Therefore, really big softboxes are a very good idea, if you have the space for them, and if they don’t get in the way of the camera.
But, smaller ones are sometimes needed too, so in a perfect world we need a range of different sizes – and different shapes."
End of copy / paste . . .
So how can you judge the quality of a softbox without trying it, and usually without actually seeing it first?
For a start, forget about who makes them or who claims to make them, which country they are allegedly made in or which name is printed on them. There's one big factory in China that makes most of them, and they happily brand them with whichever name is wanted. Some of their products are total junk, sold at extremely low factory gate prices, others are better and then there are the really top quality ones, all from the same factory - you pays your money and you takes your choice!
I spent about 10 years working with Lencarta and know that the large factories are more than capable of making whatever their customers want, at a price. It can be difficult to persuade them to use the very best materials and to make things exactly as designed by a photographer who knows what's needed, but they can and will do it if required. Unfortunately though, most sellers seem to be happy to buy their standard, cheap softboxes, get the factory to print their own name on them and sell them at premium prices - much more profit!
This particular factory used to make the very expensive Bowens range and there was nothing wrong with those except for the price. The Lencarta Redline Pro ones are made on the same production line and used to use the same materials - this has now changed to some extent because even better materials are now available. In the same small town is their closest competitor, basically a copycat. And then there's Godox, who make their own, they're cheap for a reason. And then there are hundreds (at least) of smaller softbox makers, I haven't visited all of their factories and don't know all of their products but I've never seen one that I would personally use.
I'll start out with the premise that the softbox will be used with a barebulb flash, either a studio flash head or with a flashgun that doesn't have a reflector fitted, because when a reflector is fitted to a flashgun the light hits the diffuser(s) directly and can't bounce off of the walls of the softbox, which severely restricts both the size options and the evenness of the light.
The first (and easy) way of making a judgement is on the depth of the softbox. Shallow ones take up less studio space and cost a lot less to make, but they nearly always fail to diffuse the light well. One (past) exception was the Bowens Wafer, but this was very carefully designed, very well made and very expensive. Most shallow ones are junk.
Next, look at the number of diffusers, just don't bother with any that only have a single diffuser. Elinchrom softboxes are good, but even they, years ago, sold a terrible one with a single diffuser, under their brand name 'Prolinca'.
Now look at the way that the front diffuser fits to the softbox. If it wraps around the front of the softbox, forget it, it will spill light everywhere and in many situations it will cause lens flare. If it fits with Velcro-style fastenings inside the front then that's slightly better, but you should avoid any softbox that doesn't have a deeply recessed front panel. That recess houses the honeycomb but it does far more because it also stops a lot of light going all over the place.
Next, look at the back, where the speedring is. The design will tell you whether or not a lot of light escapes at this point and if it does, walk away.
And now look at the thickness of the diffusers, the seller may or may not state the thickness and may or may not show a closeup photo of the diffusion material. They should, because the quality of the diffusers is paramount. Thin, almost transparent diffusers are useless.
And finally, does the seller offer replacement diffusers? They should, because diffusers yellow with age and need to be replaced.
