Consider the fact that illegal enterprises like drug dealers will pay a premium to launder the money (probably >=10%) and then pay taxes on the remainder. If you have the gains legally (crypto), it makes little sense to not just pay the normal taxes.
Also, if you made a significant amount of money on any crypto, you probably held it for more then a year at which point to capital gains tax is probably at most only 15% (<$441,000 ordinary income). And if you quit your job prior to selling (i.e had ordinary income <$40,000) then the capital gains would go to 0% (seems wrong (?) and maybe you would have to pay the alternative minimum tax... not quite sure).
Anyway the taxes are basically nothing compared to the benefits of having 100% clean money that can be reinvested and make 10-15% in the stock market.