…and yet…
I run a self-funded SaaS business. I regularly pay (sponsor) developers of libraries that my software depends on. These are not large amounts, but they slowly grow over time. Additionally, there are some libraries (Semantic-UI for example) that are critical for me, but have been unmaintained for a while, and I'd gladly pay significantly more, on a regular basis, to have them maintained.
I am pretty sure I am not the only one. The money is there. The problem is in gathering critical mass: both for any single developer, to make a living, and for the entire movement, so that we shift from a culture of "FREE FREE EVERYTHING IS FREE" to a more responsible and sustainable "it's free, but if you depend on it, you better contribute money every month".