I sit quite close to a large 1080p monitor. That's why I notice when the bitrate is low and the video I am seeing lacks true 1080*720 pixels. Basically it's compressed so much, that the image is noticeably worse than an image my monitor could display. That's why when I use a higher pixel count compression, like 1440p, the compression problems don't show as bad on the screen that will only show 1080p pixels anyways. That's what I am talking about. On a phone or a laptop screen it will probably be less noticeable. I guess that's why Youtube does it, it probably saves them a huge amount of bandwidth and people who want really good quality video might already have 4k displays which then get a way higher bitrate video feed anyways.

I guess the 1080p monitor size starts to be a niche. More and more people using it are on smartphones I guess so it really makes sense to have a very low bitrate.