This was by design. When the union was being formed, the small states didn't want to get steamrolled by the larger ones, so the Federal/State model was adopted.
There are laws and regulations at the federal level, but we intentionally leave a lot of this up to the states. It's a philosophy that people should be able to govern themselves.
It has its benefits and drawbacks, and I can see how it would seem silly to outsiders, but it is what it is.
It's the main reason a state like Seattle can pass it's progressive agenda without the federal approval. I think it's a very good system and promotes competition amongst states. It creates a balance. I mean, if Seattle fucks up too much, their citizens leave and another state gets to adopt that success. So, it's in their best interest to correct their errors. Or, you can end up like San Fran with priced out of entry living and shit everywhere.