KYC & AML got a lot more thorough after 9/11, at the behest of the US government. A large part of the cost is extra guarantees against terrorist funding, and it's not obvious that this extra burden is worth the cost. It's kind of like airport security, except for money.

Simply making illegal activity more burdensome with fiat money requires less effort than what's currently being spent on these processes.

There's no good reason for KYC to take days.

It's perfectly reasonable for the party receiving the funds to ask for a proof that the money didn't come from human trafficking. But that should be a fully automated process in most cases, and no one but the receiving party should have anything to say.