Liquidating the privacy coins into fiat cash is one of the biggest barrier to them because they can't stay completely anonymous while using internet at some point they will leave their traces which could be never erasable.And also not much of those criminals doesn't know the existence of cryptos that is why they prefer hard cash over banking transactions.
This is very sound and logical answer. liquidation is number one and no money trail. Because they are doing suspicious activity, they have to cover their tracks so that they cannot be trace by authority.
I agree with you. Some criminals preferred cash or physical money rather than crypto currency because I believe that some of them have no knowledge in crypto world and they might get caught with just a wrong move that they will make. This criminals just wanted an easy to use money that is why they tend to always choose fiat for a sure spendable money, anytime and anywhere.
That's another reason, cryptocurrency needs somehow a little knowledge of technology. Most of them prefer old school ways of transaction, that is preferring to use cold cash. Some are also in doubt with technology. But they are evolving and hackers and cybercrime are prevalent and rising where billions of dollars are already lost online.