Because, as aforementioned, a real battered pre-CBS Fender is liable to cost 5 or 10 times as much as a modern relic, be less suited to okayi g, particuly gigging, and have tired and crackly electrics.
The real crazy thing is that swapping out pots etc to make an old one more reliable and useable can actually devalue it. Even if you keep the original parts you can't restore the original solder, etc.
I can get it totally if people don't dig them. Taste is a very personal thing. But taste aside, most of the other reasons people trot out to justify it don't hold water.