I'm not convinced that's generally true. The form contracts language [1] clearly talks about individuals, but at least one of the DB vendor license agreements allows for individuals. https://news.ycombinator.com/item?id=15888236
If an individual were to decide to do such a benchmark, I don't immediately see how the DeWitt clause would be still valid. Not many people are going to risk that obviously.
> hese DeWitt clauses should be illegal in the United States on First Amendment ground
I agree that they shouldn't be allowed, I however fail to see how 1A applies. You willingly enter into a contract with a private entity. That contract has rules, and there are some consequences for breaking them.
I think the government has an important, and imo somewhat neglected, role in providing rules around valid contracts, but that's not 1A.