Yes, but even in those domains those projects are minorities and in many examples they make it effectively impossible to legally fund or contribute to them from the side of corporations.
I think there are very few projects that do not accept support in any form.
For a lot of single developers that's not a thing they're ready or able to do. Those that can, usually have companies established as a revenue source for their OSS project.
The need for this invoice is because companies cannot justify irrational spending. The have no process for gift-giving. There is almost nothing that will make spending on OSS not irrational, unless you're paying for specific bugfixes or customization work. You can't issue an invoice for nothing. How much would the invoice be for?
edit: that being said, please continue to make up any pretense to get OSS contributors paid if that's working for anyone.