If by any means criminals start adopting crypto in mass (especially privacy coins), we could expect a full government crackdown on the entire industry. Which is why I think it's best for criminals to continue using Fiat for the sake of the crypto/Blockchain industry's growth worldwide. But we'll never know what will happen in the future. Thoughts? 
Fraudulency is obviously observed in both fiat and Cryptocurrency, the main idea is that in fiat there are many loopholes to penetrate various elements of scam and theft such as physical or forceful acquisition in form of armed robbery, attacks on banks, pick pockets, careless in handling money, dubiousness, falsification, fake and pretendance for quality, among others.
while Cryptocurrency only has the highest victim of such to be on newbies, who don't have the full knowledge on how to identify criminality elements in disguise for promotions, free gifting of crypto, fake bounties, among others, and one can also be careless in revealing the logging credentials to wallets to the criminals.
Another interesting point is that fiat criminality can be operated by learnerd and uneducated personalities but Cryptocurrency need an expert already into crypto, skilled and equipped with digital informations, steady internet, smartness and skillful on information and technology system.
If you are scammed in crypto its as a result of your unscrupulous alertness and lack of technical know how, which the blame should be attributed to you. In a nutshell it is easier to operate fiat criminality than in crypto