Why are some laws no longer enforced?

Answer 1

The enforcement of laws is the responsibility of the Attorney General of the US or the State. Prosecutors make decision at a city or county level.

In essence, some of the laws just don't matter any more. Most of the time they aren't going to enforce foul language statutes, though it can happen. No baths on Sundays isn't enforced, but it used to be outlawed in some towns.

If society is accepting the actions, there is no reason to enforce them anymore, but they still could.

Answer 2

It depends on the specific law. Sometimes they are outdated and no one got around to repealing them. Sometimes the police/government decides that enforcement of a specific law is not a huge threat to public safety/welfare, and decides focus enforcement time and money elsewhere. Sometimes the specific law is difficult or expensive to enforce and law enforcement doesn't have the resources to do so.