Different tools for different applications I guess. Oh, and cost!
I can't see photojournalists lugging huge/heavy Pentax/Mamiya bodies & lenses around - especially today. I think that perhaps the more responsive AF and telephoto reach of the smaller cameras is better if you're a sports/wildlife professional. MF quality is going to win out in slower environments (studio/landscape). Different professionals will have different requirements.
Personally, I use medium format because of the quality, and I reach for my 35mm cameras when I want portability.
Medium format is a preferred option when you need extra quality or larger prints. For a 10x8 in a photo frame there's little difference once viewed from a bit of a distance though . I also used to get a bit more tonal range if used correctly on my Hasselblad when I did wedding photography.
I use them when I want to do serious photography (rather than snapshots with a digital camera) and need something faster to use than large format. I can certainly see the difference in prints from 35mm and MF and avoid 35mm. The smaller number of frames on a film doesn't worry me as I don't usually make many exposures.
i had a bronica 6x6 then a fuji 67...
i got them as i wanted to try to sell photos...trannys...spent a load of money on film and mounts...
it was a phase for me really thinking i would get some cash to cover the outlays
processing was by labs
when digital came...i was better pleased just doing pp
i will say though the 67 results blew me away....great lenses in those fuji's
There was a time when the choice was simple: 5x4 for studio work; 6x6 for press and weddings; 35mm for journalism. As time went on better film and chemistry changed the emphasis towards 35mm which was cheaper to run and lighter to carry. This is the system I was carrying around in 1972...
Way back, I was offered a Hassablad 500c, with lenses, for a couple of hundred quid... gawd the opportunities we pass over.. b-u-t, I had the thing on approval for a week or so, so just out of interest, I bought some, I think Ilford 400, in 120 and in 35mm and went and took some back to back comparison shots, that I then processed and printed myself.
My conclusion, after blowing up minuscule crops of the same picture from 35mm and 120, was... 'Oh-Kay... yeah there IS a difference... just, and the Hasy is the better... IF you enlarge a postage stamp to the size of a barn door..... Good, yes. Practical no. For me, out and about, the IQ obtainable from hallf decent 35mm kit was always going to be good enough, and the outlay to swap systems plus the overhead of more expensive film and processing, was just the start of the arguments 'against'.
A few years later, I was given my Gt Uncle's 6x9 Ziess Ikonta Folder, and not long after my Grandad's Kodak Retinette 35mm. These had been the subject of much protracted argument between the two, in my childhood; Grandad raving about 35mm, and how he could take 36 frames, IN COLOUR, wow! And my Uncle could only get I think 6 B&W frames for his roll of film. Playing with both cameras, now in my collection, they were, err, both right, and both wrong!
Uncle John's arguments for the Ikonta, are probably the more valid. With a 6x9 negative, he could on a week-end, load up a roll of B&W, expose it all, conservatively, take it home, and make contact prints to go in the family album at the kitchen sink, over-night, and 'The Family' could have pictures to look at over Sunday Lunch, for 'about' what my Grandad paid for a 36exp roll of slide film... which we never got to see, cos the projector bulb was always blown, which was probably small mercy considering the 'Faff' he went to setting up a tripod and waving a selenium cell meter around, but still.....
It was swings and roundabouts thirty years ago, and no clear winner on either quality of cost. Not a lot has changed, apart form Widgetal.
So the short answer is I have MF, I do NOT choose to use it over 35mm, let alone digital, very often, if at all. I DO pick the old TTL swing-needle Sigmas film camera and M42 screw 'prime lenses; over the Digital, but, has nothing to do with potential IQ. Its all about the user involvement, and the 'extra' involvement of faffing with 120 and a hand held meter, IS frankly one faff too far for my taste!
In that time I have rarely made a paper 'print' let alone a large scale enlargement, from film of any format, let alone an electric-picture-maker, and my opinion is largely unchanged. YES, Medium format offers wonderful image quality, 35mm and latterly Widgetal, a heck of a lot of convenience, and 'EYE' am never going to exploit the higher IQ that MF may have; heck, I probably have never really exploited the full IQ that can be got from the half decent 35mm gear I have, so I sure as eggs, don't really miss not having that potential quality to wast in Digital.... and I certainly don't regret not paying fort the privilege of having it to wast!
So, I do have some MF gear. I have used a lot more... b-u-t... it's just not something that means much to me, or has ultimately been worth the candle, though I can appreciate it, and see why for some it might be near essential... but for me its only of passing interest, and I keep looking at that old Ikonta, then decide that whilst it may be 'fun' to go use, I would do as well loading up the Retinette and using that for the same level of involvement and faff, then I pick up 'something' that has a battery in it, if only for the in view-finder light meter, if not an CCD array.... 'cos ultimately, there's only so much 'faff' I can stand, before the fun of it wears off.