Uhhhh...actually, it benefits the black marketeer more than it benefits the average Joe. And this is where we enter a somewhat thorny zone, relating to the fate of the United States and other advanced economies.

Do you think that Donald Trump is a monster? Do you think his plan to build a wall for which "Mexico will pay for it" via confiscating remittances is monstrous? If so, then you're implicitly rooting for illegal immigrants to join a black market - a black market for remittances.

Do you think that the cashless society would be an Edward-Snowden nightmare? If so, then you're implicitly rooting for ordinary Joes to (partially) join a black market - a black market for regular goods and services that the future authorities have red-flagged. Those "regular goods and services" might be as innocuous as certain frowned-upon books. Look at the mileage that Bill Nye the Censor Guy has gotten for his proposal to jail "deniers."

It's speculative political questions like these which keep me interested in Monero. I could be wrong, and I admit that I'm a sucker for certain varieties of declinism. But all is not well in Pleasantville, and Monero - even if its use cases are solely confined to "real" black markets - can be seen as a kind of escape hatch for ordinary Joes if they need to hide what they do with their money.