My guess is a lack of political will to do so. It's hard enough to get new political agendas passed in some cases without the added burden of trying to introduce something to take care of a law that is currently unenforceable, and would also appear to be unenforceable post removal of protection from the consequences of that law.

My second guess, and it could be mixed with my first, is that unless you have a really solid party majority you could be inviting a voter response for tackling a wedge issue and it might not be perceived as worth it if the law is unenforceable anyway.

Other stuff to worry about than old laws that no one enforced. Like how in PA it's illegal to sing in the bathtub

They tend to revisit old laws as they come up. Times and opinions change, someone charged asks “wait, isn’t this law bullshit?” and then it’s time to look things over. ‘If it ain’t broke, don’t fix it’ is the general attitude, but with these old laws you don’t always know shit’s broke until someone’s inconvenienced.

Because there’s no reason to, especially something like an ancient law that was technically invalidated by a Supreme Court case. There are invalid laws on the books basically everywhere, lots of states and many more counties and municipalities, because there’s no real benefit to legislatively repealing or rewriting a law that’s been invalidated by a court, except to make less (billable) work for lawyers. Since most legislators are also lawyers, why would they put in extra work themselves that serves no purpose but to make it harder for their colleagues to earn a living?