Widespread adoption doesn't seem to be a goal, but really as long as the POSIX APIs are supported in a reasonable manner (...or you are Windows), it doesn't matter much. It's nice to use, and it gets to take advantage of portable open-source software which gives it a larger community of developers than (say) Plan 9 and Amiga enjoy, so market percentage doesn't matter much.
My appreciation for it is that it has been a long, long, long labor of love for its developers.
I can't help but to admire the dedication of everyone who made it happen. I don't think that widespread adoption was anything they had in mind.