I believe the idea is that you don't care what language is being used if you aren't going to look at it anyway. Given that premise, the AI can write JavaScript instead of something you need to compile separately.

WASM is hard enough to use that I would say the number of people using it just because they don't like JS/TS is fairly small.

At least that's always been my impression. If you're willing to go through the effort to use it, it's probably because you need the performance gains, and AI hasn't changed that.