It is DRM, and Amazon Prime is particularly bad, it servers 540p or similar - it is basically unwatchable (other streaming services default to 720p, which is OK, with netflix having an unofficial plugin that makes it 1080p).

And I was thinking I'll watch The Boys in nice quality on official streaming service, turned out I had to cancel Prime and download 2160p torrent. I'm still puzzling what DRM solves, in most cases it pushes me into torrenting.