Newspaper article detailing the Top 20 Best Selling Phones in History.
Saw this article from The Telegraph, detailing the top 20 phones ever sold according to Wikipedia.
It seems "cheapness" sells more than security.
Cheap sells, because most people are not rich. Most of these phones (the feature phones) were not really that insecure because you could not do a lot with them. I still have a feature phones, and I will keep it, until the Ubuntu port for the Fairphone 2 is mature..