If that were true then why is every DRM play not designed around cutting down piracy, but on limiting the rights of legal purchasers?

Why hasn't there ever been key-transfer features to facilitate sales/trades/loans? Why are there always platform locks and media locks and account locks? Why is there so much effort to stop legal backups, loaning, libraries, etc?

I don't doubt individual good people or divisions exist in major media companies that would just as well sell a movie for $20 and be done with it. But the repeated DRM strategy does not jive with that at all.