Because the market for pirated movies is larger than the market for pirated music. Movies will be popular worldwide and thus will be pirated more than music, which depending on what kind of music it is wouldn’t be as popular in every spot of the world. That’s my guess.
At least that is what I hear about Handbrake, I, of course, do not have any personal experience since I do not use it because it is illegal to copy my own property and I would not want to break the law.
It’s legal. It’s just that the DVD companies intentionally make it as difficult as possible.
The standard for CDs came out at a time when people having 1GB of hard disk space and the processing power to copy a CD was a laughable concept. The standard for DVDs came out after the movie industry had learned from the mistakes of the music industry.