Congress is really slow/bad at updating laws. State legislatures tend to be a lot more nimble (not as partisan, as there isn't as much focus on them. Plus many states of super-majorities, so it is easier to pass things if all members of a party agree).

I'm fully for most laws being tested at the state level before the federal gov gets involved at all (unless it's interstate commerce). Honestly, I prefer the fed staying out of most things and letting states handle it.