Most likely you're watching in 720p. In Chrome, Firefox and Opera you're getting 720p max. To get 1080p you need to be watching in Internet Explorer, Safari or on a Chromebook. To get 4k you need to be watching in Edge and have a 7xxx or 8xxx Intel CPU and HDCP 2.2 enabled display. Source:
One of the more interesting theories I've heard is the link between the housing crisis and the retail crisis. When you live in a tiny shoebox, the last thing you need is more stuff. Back in the days people had comparatively huge houses all to themselves, and could buy crap to their heart's content.