I asked a question about this too. Many people just ask tonnes of questions that are either ridiculously cliché or just pointless. You'll tend to find that these questions are, by the most part, asked by non-native English speakers or spammers. These are mainly the accounts that are purely to make money and writing is seen as purely an income-based activity. I have also seen some that claim that the numerous questions are to increase their grasp of English language, but I am very scepticle.
Asking multiple questions is a way for them to increase their visability in an attempt to gain followers, hits etc. I don't think that there is much evidence to support the idea that it boosts Hubber score, but then again HubPages have never disclosed their algorithm. Hope this helps.