Very few people would even have the knowledge of who, how, or where to "sell" such vulnerabilities. Going through a public bounty program is pretty much always preferable.
Most people don't want to be felons.
I am sure this is a crime, but what crime?
I think people who can hack, also know where they can sell it
Don't worry, as more and more people get put of of work by AI the number of people willing to be felons will increase. Hell, they might even become president.