So, you may or may not know that, but you need FreeBSD and OpenBSD and they also need you! Every cent counts and so does every contributor, that helps the foundations keep their non-profit status.
Likewise I shouldn't need to know Netflix uses FreeBSD, or the PS4 uses it, or Nintendo uses it. My users don't know my software runs on Heroku, they're not being asked to give money to DHH for Rails or become a Postgres sponsor or donate to the Linux Foundation just because they use a product that uses that technology on the back end.
If you make a product that directly profits from the work of a non-profit, you should consider a donation to keep the project around. But if you just use a product that's built on an open source project in a non-transparent way and don't actually use the open-source project yourself but you're still donating to it, you would be a very generous citizen.
If FreeBSD didn't exist, Nintendo and Sony and Netflix would use something else. If companies that use FreeBSD want to keep using FreeBSD, they're the ones who should be paying for it.
It's a little much to ask that everyone donate to every open-source project they happen to use in an incredibly incidental way. I'd be spending half my time hunting down projects and the other half cutting checks to them. I donate to projects I actually use.