In practice, you're not finding a bug like this every week.
The bug bounty programs were originally intended to give a white hat market alternative to the black hat and gray hat markets. They don't do that. If I find a bug, and I want profit, I'm much better off selling to my government than to Google.
One can only imagine the number of exploits the US, China, Russia, North Korea, etc. have in their cyber-warfare vaults.
Exploits compound. Often, two minor exploits make a major exploit.