Consider: today I might be working on FOSS. But maybe tomorrow a friend asks me to help him with his (small) business, by e.g. adding a little bit of automation. Suddenly, all my knowledge and experience of GPL-ed libraries goes to waste, as I won't be able to use any of that to help my friend.
Given two equivalent libraries, one on GPL and one on MIT, I'll always go for the one on MIT. MIT, BSD, etc. seem to be the libraries that give you most options (I'd say freedom, but that's not how GPL sees freedom) while still maintaining the integrity of the library itself. Those are the licenses that best and at the same time satisfy the needs of developers who are not in it for money, and users who don't want to waste their brain cycles on going through possible legal scenarios around all their actual and imagined use cases.