I think a bigger reason is all of those is the brand trust that YouTube has. If I, as an independent director, make a music video, or a 10-minute tutorial video, or a short cinematic film, and want it to be seen by tens of thousands of people this month, YouTube is where I'm posting it. If you can persuade me that there's a video URL that thousands and even millions of random strangers would be even more likely to click on than one that starts with YouTube.com, I'd be very grateful to know it. Even Vimeo is known to far fewer Gen Z viewers than it has been to Millennials -
https://trends.google.com/trends/explore?date=all&geo=US&q=v...