The underlying motivation of the encryption on DVD's goes beyond preventing piracy. It's about making sure you cannot skip past the ads at the start of the movie. They needed a mechanism to require all DVD players to respect the flags on a DVD that say "this cannot be skipped", and did that by pushing it into the 1996 WIPO treaty that you must have anti-circumvention laws that prohibit people from breaking the encryption on copyrighted materials without the permission of the rights holder. Only licensed players are decrypting with permission. VLC is not a licensed player, so VLC often runs afoul of such laws.

Just because the patents expire doesn't make the anti-circumvention laws go away. Those laws only stop applying once the copyright on the DVD expires, in a century or so.