all good points. i also think what really pushes a lot of developers to do open source, and bear with me for the unpopular opinion--is ego. they love having followers, and a voice on twitter with some open source badge on their profile page. it's in a way a status symbol of "i did this important thing that a lot of people rely on, im pretty important." i highly doubt that even 5% of contributors are doing it out of the kindness of their hearts or the community.
you can sort of see evidence of this within repositories filled with smug comments within the issues or pull requests
you can sort of see evidence of this within repositories filled with smug comments within the issues or pull requests