Why is this still a crime?

Because the states never took it off the books after the Supreme Court invalidated such laws.

Lawrence v. Texas (2003) held that private (non-commercial) sexual relations between consenting adults were not subject to state regulation and could not be made criminal.

That the participants are "consenting" is not the relevant issue. The issue is whether the conduct poses a threat to the greater society. When these archaic laws were passed, apparently they were considered a threat. But it is unwise to pass laws that are utterly unenforceable, anywhere and at any time: they make law seem ridiculous and inept - which is not conducive to achieving the objectives of law.

These laws are never enforced. When someone tries to enforce it, that's when the laws get stricken. Otherwise, no one's going to take a stand to "go easier on the gays" by proposing to eliminate such a law. In the states where this is true, that would be political suicide.

its usually not in forced unless someone is not of the age of consent ,and that age varies from state to state. laws are like locks on doors they keep honest people honest

It is not necessary to remove a law that is no longer applicable and in some cases it may be impossible to get enough votes to do so because of majority rules, in other words how many votes have to there to erase that law.

Precisely. Still on the books; nobody really cares in practice.