High resolution video is nicer to watch when:

1. The content is worthy of it. (So, you know, not some talking head sitting at a desk like your average Youtuber.)
2. You have so much free bandwidth that spending an order of magnitude more to get a marginal visible increase in quality is worth it to you.

480p hits a decent balance for me in most cases. It makes the people in the video recognizable (like, say, the presenter in a news/comedy/pop science/whatever vlog), and most text in such a video will be readable. Sometimes when there’s a lot of diagrams or when the pictures need clarity I’ll boost it to 720p, but using up over double the bandwidth is just not worth it most times. I have more important things to do with that bandwidth.

For a movie with a lot of rich detail, etc, 1080p is even nicer. It might even be worth the five times the bandwidth to get to it. But here’s where diminishing returns starts to kick in. 1080p is five times the bandwidth, but only a bit over twice the linear resolution. It had better be a really important doubling of resolution.

4K streaming? That’s laughable. Yes it’s over 4 times as high in linear resolution, but it’s over TWENTY times as high in bandwidth. I could literally watch 20 simultaneous 480p streams (or 4 simultaneous 1080p streams at a paltry 2× improvement in linear resolution) for a single 4K stream.

And that’s just bandwidth. Processing costs are on a similar order of magnitude. I have a computer at home that outpowers all the supercomputers that were on the planet put together when I was a child. Playing a single 4K movie sucks up most of its processing power. Again, I have better things to spend my CPU time (and/or electricity bill) on than watching some presenter’s pimples on screen in fine detail.