As of late, crypto has become extremely popular due to the negative effects of COVID-19 in the mainstream economy. People are starting to consider crypto to be a safe-haven against the traditional monetary system empowered by banks worldwide. Yet, the vast majority still relies on Fiat for day-to-day transactions because of its price stability and widespread acceptance in the mainstream world.
With the advent of privacy coins, people can enjoy true financial freedom like never before. Privacy coins can become attractive tools for illicit activities because of their untraceable blockchain ledger. Despite all of the benefits privacy coins provide, criminals still rely on Fiat for all of their nefarious actions. I'm starting to wonder why, since Fiat (physical cash) is not as anonymous as one thought it would be. Privacy coins are truly anonymous (especially those that are private by default like Monero and Grin), as there is no central authority behind them. Maybe criminals prefer Fiat because of its high level of adoption in the mainstream world? Or maybe because Fiat has an easier learning curve than crypto?
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?

Indeed true that privacy coins keeps them from being identified since it is anonymous but when the time comes that they need to convert their coins into fiat currency then that time they are no longer anonymous because transactions like that needs proper identification to convert it into cash. But there are still some loopholes that they can use because the system itself is flawed.
Still they can't make a stronghold within the crypto space because they know there will be a time that the government will and eventually can crack them. So instead of privacy coins they still prefer fiat so some various reasons.