Why does plex have subscriptions at all? I understand (at least theoretically) that not all software is free, but charging for it the normal way (you pay money

Why does plex have subscriptions at all? I understand (at least theoretically) that not all software is free, but charging for it the normal way (you pay money and buy a copy that you then use without it phoning home) works perfectly well too. Anyway I had had the impression that Plex also sends at least the metadata of your video library to its home server. I didn't realize Kodi was XBMC or that you could build it yourself. Thanks for that info.