Editors will tell you that a huge percentage of self published books are crap. That may well be true. But it's also true that one person's crap can be someone else's thrilling read. If ebooks offer a way to find a readership, that might be enough for a lot of writers.
Books without editors will not be as polished, but it's possible that a good percentage of readers won't actually notice that. Who was it that said no one ever went broke underestimating the taste (or was it intelligence?) of the American public? Whoever said it, it appears that Mr. Barnes and Mr. Noble were listening.