Think about it.

Those laws were written long before VHS was a thing. Back in the day they were policing burlesque shows where the ladies might go down to G-string and pasties. The pubic hair thing was a simple test to see if they'd gone too far.

Also, in the bars the dancers might have to keep their G-strings on [laws vary by state] A lot of dancers travel, so it makes sense to be ready for the strictest enforcement