Your last sentence while intuitively seems true, simply isn't. There are plenty reasons some one might contribute to a project, the language could be the only reason, and that would be completely reasonable.
Example: You might not be interested in writing a text editor, but you've seen this and the lime project, both written in Go, you don't care for writing a text editor, but you might figure you could spend some time to this guy fix an issue in your free time.
Is the above a little far-fetched? Maybe, is it unrealistic? Not really.
Example: You might not be interested in writing a text editor, but you've seen this and the lime project, both written in Go, you don't care for writing a text editor, but you might figure you could spend some time to this guy fix an issue in your free time.
Is the above a little far-fetched? Maybe, is it unrealistic? Not really.