In their wisdom they didn't, and we're stuck with what they actually set into law. Not guessing at their intentions, not inferences, but the actual letter of the law. And the Constitution says that if the government isn't given the specific powers to regulate it, the government has to stay out.
The real beef I think you have is with the 14th Amendment, applying the Bill of Rights to the states. But as I said above, the Bill of Rights *has* to apply to states, or the rights it acknowledges are meaningless.
The government could do an end run around freedom of the press by having a state or municipal government shut down an opposition newspaper if states aren't bound by the Bill of Rights. The government could prohibit gun ownership by enforcing it through states if states aren't bound by the Bill of Rights.
I don't care what consenting adults to on their own property. But as I've said above, I value freedom. That includes the freedom to do things I wouldn't personally do, as I don't expect the government to force all citizens to conform to my personal preferences.
Please point us in the general direction to the Constitution (or any other official U.S document) preferably one that specifically states that citizens are exempt from any state criminal law. Precisely, the states laws that criminalize homosexual sodomy.
Article and section please.