Because this stuff was already extremely complicated before AI came along.

For example, the thing you are actually dealing with isn’t copyright or trademark here, but “right of publicity” which relates to the right to one’s likeness for commercial purposes.

Which isn’t protected federally in the US and comes down to a state-by-state basis.

There were instances where you had humans impersonators mimicking voice or likeness of others for years before AI. Or even using old materials and re-editing them like Issac Hayes’ voice for Chef after the falling out with the South Park creators over their Scientology episode, where they subsequently had his character fully voiced as he joined a pedophile club.

Laws are usually a reactions to a behavior we want to eliminate, they’re rarely made to prevent something we anticipate.

I’m pretty sure there’s a Black Mirror episode all about this.

There is already laws regarding impersonation and the right to your own image.

So not sure why AI would make it different from a costume or a drawing

Basically, governments and laws can be fairly slow to adapt. Consider that it wasn’t that long ago that you could absolutely tell that something was made by AI whether it was caused by stilted/unnatural speech or mangled fingers in fake pictures of people. In a few short months we’ve gone from dreamlike hallucinations of real things, to almost passable renditions. AI is just advancing too fast for most governments to make a decision and formulate a coherent and mostly future proof set of laws regarding it.