Time is money- plenty of people would trade $200 for not having to spend time doing that. That's the sort of thing that's really fun and cool and interesting if someone's a hobbyist and/or student and/or in the larval hacker stage, but at some point in life after spending decades having to make sure their hardware is supported by Linux/FreeBSD/whatever, the bloom can come off that rose pretty hard and it's a blessing to just give someone money to worry about something you don't want (or don't have the time) to spend time doing.

Of course, plenty of people do have plenty of time to read HOWTOs and hardware compatibility lists and so on and still enjoy doing so- more power to them. Especially if $200 (or whatever) is still a meaningful amount of money to them that they need for other things. But I've always felt that a big reason why so many people advocate that approach and present it as a rational choice is because they themselves enjoy doing that and would do it anyway regardless of the time/money tradeoff.