The use case of PiP is legit but I agree it doesn't make a lot of sense for the browser. However, many users do not have proper native media players that would

The use case of PiP is legit but I agree it doesn't make a lot of sense for the browser. However, many users do not have proper native media players that would provide the same functionality so I can see why browsers might want to implement it for the casual users. A native media player with youtube-dl is still king for power users.