Why? Why is so important to you that everybody live the same way?
It's not so much that everyone live the same way its to make life easier if you were to travel from state to state. The ability of rapid travel that has come about in the past century have made some state laws almost moot in point.
Lets use CCW as an example. You live in state A, this state has laws making it easy to have a CCW. You know that your state has a reciprocation agreement with most other sates that makes your CCW permit good there.
You travel via car to state B, state B has a bunch of gun hating people in its legislative body and unbeknown to you repealed it's reciprocation agreement.
You get pulled over for speeding, and the officer asks if you have any weapons. You volunteer your CCW and are promptly arrested on weapons charges.
An overarching federal law forcing universal CCW reciprocation could of prevented it.