The basis for the ranking was a cumulative tracking of benchmark results that were required as part of commissioning bespoke computers. A contract would be written to buy a computer that could achieve a certain performance in operations per second, and in order to satisfy that the benchmarks were agreed to and codified in the contracts. Government contracts are to a certain extent public information so the goals and clout of successive performance were tracked in this way.

If you don’t need to satisfy a government contract, or don’t need the clout to attract engineers or funding, submitting results draws unwanted attention to what you’re cooking up.