Well, often you get way more than you pay for, and it would be stupid not to acknowledge that. For example almost all Linux users never pay for nor support Kernel development in any way or form. And I think the people who do the development and create the value for the rest of us mostly are ok with that.

That doesn't negate the fact that when you rely on open source software for your business and need more than just read access to the repo it would be polite to wise up on the maintainership status of the project and ask if you can contribute back in any form.