I agree Richard Hipp should be compensated but he explicitly licensed and releases SQLite under a public domain license: https://www.sqlite.org/copyright.html Not Apache, not MIT, not GPL... public domain. You can do almost anything with it and not be beholden to any demands. You can tell people you built your business on SQLite... or not. It's public domain.
Sure, but Apache, MIT, and GPL licenses don't require payment to the author either. That's why it's up to the company to decide to offer compensation without being required to, and why I'm curious which companies actually do it.
It's like when RedHat when public and offered pre-IPO stock to open source developers.
That said SQLite has a business model of selling support and premium features like encryption: https://www.sqlite.org/prosupport.html