Criminals paid in cryptocurrency need to receive their final payout in cash. This requires obscuring where their funds come from. Unfortunately, several sophisticated services and tools help criminals do so. After all, if there were no way for bad actors to cash out cryptocurrency that they had received through illegal means, then there would be far less incentive for them to commit crimes in the first place.
That is probably the greater risk for criminals, after all if you want to obtain fiat currency for your bitcoin most likely you will have to identify yourself, however what will happen when they can finally use their bitcoin to buy whatever they want by just using bitcoin without converting to fiat? Most likely at that point it will become impossible for anyone to catch them if they are smart and this is unfortunate as it will become impossible to recover the funds stolen in scams or hacks.
This is life... Criminals are exactly like us, they just make a different living... If they can use bitcoins everywhere, it will be better and more convenient for us to use bitcoins too!
By the way, now it is also unrealistic to return stolen funds... So I don't think that anything will change much if the bitcoins are accepted all over the world!