I think it’s more than that, because he flipped on Abortion (which led to that infamous public refusal for Communion by a crazy Southern Priest)
I think it’s a “political capital” thing. Even if it’s not a high cost, it’s just not a priority for him to spend time, effort, and favors to push it across the finish line Federally when it’s bound to happen on its own eventually.
He pardoned (almost?) everyone in jail for simple possession and ordered the DEA and DOJ not to pursue or prosecute possession. He basically “cheaper method” decriminalized it. And it kinda makes sense. What’s the next president going to do? Waste all their political capital re-igniting a drug-war that nobody wants? They’re gonna do what he did with the SALT changes. Let it ride despite the fact some people are pissed because nobody will be THAT pissed at “let it ride”. And for the same reason - they won’t really care.