There is those "tire pressure checker" metal bats, which are clearly self-defense tools, but heavily branded all over them that they're used to tap tires to hear a "thump" to know if you've lost significant tire pressure or not.

There's entire industries built around "never admit to carrying a weapon even for self-defense". Which says that the law around it simply isn't working as it should: It is not effective, AND it is being actively circumvented.