In response to your first point, I'd rather use and contribute to FOSS that supports a SaaS or proprietary product. Issues are more likely to be addressed if the maintainers depend on the software themselves for profit. I see it as trading helping them improve their software for the ability to use it in my own projects. It also gives some reassurance that the FOSS is going to be maintained if the creators depend on it financially.

I agree with your second point though. The main reason I see for contributing to FOSS is to fix issues that affect me or creating issues that may lead to the maintainers improving the software in a way that would benefit me.

I think it makes sense for companies to open source tools they depend on. They help others by providing the free software and in return they get help identifying and fixing bugs.