>pays for real expenses
Only a small percentage of donations do.
>instead of whatever vanity project
Anytime the topic of Wikimedia donations come up you will see people complaining about their vanity projects too, wishing they could donate towards wikipedia itself.
Not the person you are replying to, and it is a bit tangential, but you just basically described a solid chunk of open-source software work.
I am not mocking open-source software work, I am mocking how reductionist the parent comment was, because their logic often applies to volunteer open-source software work as well. And, I suspect, on HN we can agree that volunteer open-source software work can often be worth doing, regardless of how "irrational" it is or how much for-profit corporations could benefit from it.