In today's world of excess and mass production of products, many of which are not needed, all of which end up in the landfills at some point, not to mention the huge disparity among the rich and poor, capitalism, blah blah blah, should shoplifting even be a crime (anymore)? Especially compared to the more serious crimes?
To listen while using other apps, switch the player to Picture-in-Picture (PiP) during playback — it keeps playing in a small floating window (the screen stays on).
To listen with the screen fully off, in-browser playback stops by YouTube's design. Open the video in the YouTube app to keep listening where background playback is supported (e.g. with YouTube Premium).
Open in YouTube app