Maybe those criminal's doesn't know yet about crypto or it is easy for them to use the fiat money which is used of all people in everyday lives instead of putting their time on learning in cryptocurrency. Also they prefer the money that they can easily spend without any transaction to make like in cryptocurrency.
Yeah it might the case that cyber criminals love crypto currencies but for the average criminal the education in IT and internet issue is probably very low and they will not trust any cryptos. I would assume that they will value cash always the highest, because they can see and touch it. Also when paying with cash you are more independent. When paying with cprytos you need internet access and government might track you.