I know what you're saying, but that's not a great example. In the right crowd, cocaine is very fungible. So to your point, if gov makes crypto illegal will it still be difficult to use in black markets? Idk
What if the person you sell cocaine to for dollars to spend on Amazon reports you?
What if you get an IRS audit, how do you justify the funds used to buy the house?
Yes, you'll be able to use crypto on black markets, but that is hardly covering all your needs.
A drug dealer certainly could.