Because "just posting on youtube" doesn't actually characterize what people are actually doing.
So for instance: why do I pay attention to some reviewers on youtube?
I find audio gear interesting, and there's tons of stuff I'd love to hear, even if not to own.
There are a number of youtubers who are acquiring a ton of different speakers, amps etc, many of which I find interesting. So I would like to hear about their experience with that gear. And again it's not "just posting a video." That is downplaying the amount of work involved. These are people who have to go about aquiring tons of gear, shipping and receiving it, going through all the unpacking and re-packing of the gear, getting info about the gear, setting up and listening to the gear, testing it in various ways, often doing comparisons with other gear they have on hand, or had also tested, putting the time in to the video production, graphics etc. And more reviewers seem to also be incorporating some level of measurements, even if it's room measurements of speakers. All of this work goes in to producing a video so that I can see this gear and learn *something* about it, or even just be entertained by the results. And if a reviewer seems to be accurate in describing speakers I'm familiar with, it gives me some more confidence on his/her take on other speakers. I know many on ASR disregard anything any non-ASR-approved reviewer says about gear, but I don't. I don't just believe everything they say: I can wend my way through unlikely claims vs plausible claims.
So, sure, I get it: it's not your bag. But there's a hell of a lot more that goes in to producing the review videos than just 'posting anything on youtube.'
I get to see a TON of gear on these videos, at no cost to me, and at the expense of all their effort. I'm good with that. (And they should be able to make money off their effort: if that's what it takes to put up the videos, good on them).