Well, I can't answer for other people, but if you read Private Eye you'll see lots of accounts of money being wasted (or siphoned off) to organisations that allegedly shouldn't get it...
But, I don't think that that's the point, there will always be mismanagement and corruption in public life.
The point, as I see it, is that there should be a level playing field, in which all sellers of both services and equipment play by the same rules, and the simple fact of the matter is that neither Amazon nor Ebay seem to be doing much to stop overseas sellers evading both VAT and import duty, and anyone who buys from them is adding to the problems, starving our country of revenue and making it impossible for legitimate sellers to pricematch.
And it doesn't help when some manufacturers care nothing about customer service, and whilst fixing their own factory prices at a very high level, allow dodgy sellers to sell at prices that allow either a modest profit (when paying taxes) or customer service, but not both.