Allow me to disagree. While I myself use Ubuntu as my main desktop PC, I can totally see how Android makes more sense for a lot of customers.
Don't forget who this is aimed for. Alas, Ubuntu is still mostly for folks above some level of computer proficiency. Android, on the other hand, is probably one of the most "familiar" experiences for people using smartphones, and the (huge) amount of applications is easily accessible through the Play store with lots of reviews and hence high quality. You just don't get that for Ubuntu.
Don't forget who this is aimed for. Alas, Ubuntu is still mostly for folks above some level of computer proficiency. Android, on the other hand, is probably one of the most "familiar" experiences for people using smartphones, and the (huge) amount of applications is easily accessible through the Play store with lots of reviews and hence high quality. You just don't get that for Ubuntu.