If I owned Hubpages and I saw lots of low quality material but I knew that it was original and not copied then I would not want to delete it. The reason for not deleting it is I know that low quality stuff can go to the first page of google. I have a website with over 260 pages of original stuff and my worst page is on the first page of google in a high position.
Google makes up the rules about what quality is and according to their ranking system the Tumblr Blog (an example) is authoritative with a Page Rank 8 and getting more powerful while Hubpages is a mere Page rank 6. Tumblr does not have high quality writing because it was not designed for that. It has also has tons of duplicated content by reblogging. Hubpages probably has a really hard time sifting quality and at the same time doing things that don't compromise their site popularity with Google. Since the Panda update, Google has been scoring people very erratically and people who run large websites know that it is simply a game and that Google recommendations are made to divert people from the fact that they can't keep everyone happy forever.
The conclusion I made is that if you really do have a super quality site it means nothing to Google. It might mean something to real people who need it but remember that Google is a machine and not a person. Why is Youtube still so popular with a Page Rank 9 when it is loaded lots of trash? Go figure!