More importantly, music is typically available in non-protected form.
As a rule, I listen to stuff on Spotify and buy what I like on good-old-CDs. Typically, this means that I discover an artist or band and order half-to-all of their entire discography at once and continue to follow them, afterwards. CDs are trivially easy to rip to FLAC and those files can be played anywhere, always, offline and even converted to aac for mobile devices with limited storage.
The same cannot be said for movies. If I buy a blu-ray movie, I can't easily rip it to play on my phone while travelling. Buying a physical copy of a movie is just another way to "rent" it; there is NO way to actually BUY a movie.
Conclusion: I never buy movies and almost never watch them, either. Just couldn't be bothered.