There are many issues on which not everyone agrees what should be done. If the federal government does them, the same solution is forced on everyone even if a large plurality of people would prefer something else and those people constitute the majority of various states, so it makes more sense to let each state decide for themselves. There is nothing stopping them from all doing the same thing if there was consensus.
And when there isn't consensus, you get to see how each of the alternatives turn out when different states do different things:
https://en.wikipedia.org/wiki/Laboratories_of_democracy
But if the federal government is even allowed to do them then whichever faction has the federal majority imposes their will on everyone else and prevents that from happening.
> Talking about "breaking the rules" in this context
The post I responded to was the one that brought up "breaking the rules". My point is that you should follow the rules if you want to complain about others breaking them.