Lately, I see a lot this behavior and I hate it with all my strength.
Say I'm watching a video (e.g. on Twitter) but the only thing that interests me is the audio. I keep going with my twitter (or whatever) thing, but when I scroll until the video touches the screen border the audio gets silenced.
Ok, I get it. I put it again, let the scroll where it wants to be, and start working on another tab. Surprise! The audio gets muted again.
I think this is horrible by itself, but to make things YET worse, the damn video keeps playing, so if I want to keep hearing it, I have to search for the position I was in, which is bad enough in an FHD computer screen but is really terrible in a smartphone.
Why is this so prevalent? Is this considered to be good UX? Something I'm missing there?