> subtitles can work but it's basically a second language

That argument applies just as equally to sign language - most countries have their own idiosyncratic sign language. (ASL, LSE, etc.). Any televised event that has interpreters will be using the national language version.

The closest thing you're thinking of is IS - International Sign but its much more limited in terms of expression and not every deaf person knows it.

> there's not really a widely accepted written form of sign language.

Because it makes no sense to have it unless there was a regional deaf community that was fluent in sign language and also simultaneously illiterate.

https://www.reddit.com/r/NoStupidQuestions/comments/6t7k1w/h...