I think it's more related to how "normalized" it is. You don't really view wc as solving a problem you had - you view it as something that's always been there. It's worked for decades, and will likely continue to work for decades.
People are only likely to donate to something that's solving a problem they care about.
I use wc but I don't donate to GNU/FSF (I'm sure some people do but almost no one I know does).
(just using `wc` as an example -- I'm well aware that `curl`'s utility is much greater. I use curl once in a while.)