360p vs 480p has nothing to do with quality*. It is how the encoding is done. Bitrate and other settings (mainly bitrate) can produce bad picture quality if it is too low in relation to the amount of movement on screen. A low bitrate can be used if the video is just a static view of a wall or flower or even a person that isn’t moving. Higher bitrates are required for motion, even higher bitrates for faster motion. This is the key principal to Variable bitrates.
What is most likely happening is that people out there are trying to be the first to get titles in the wild (WITH all of theirs ads and garbage!) before the other guy, so they probably encode as fast as they can with lower bitrates to produce smaller files (because usually fast encoding settings use high bitrates producing larger files).
* but that depends on how you view them. You can have perfect looking pictures of both 360p and 480p when viewed at their respective resolutions but when blown up to your 1080p (or higher!) resolution monitor, yes, the 480p will have a slightly better looking picture than the 360p.