Most of the "reasons" being money. Android phones are mostly sold to the "unwashed masses" who just want a cheap phone and get some low/medium spec Android phone with their contract. You cannot really compare something sold in 200 models and 50 price points to something sold in 5 models and 5 price points. It will be like saying people buy more Toyotas than Mercedes. Well, of course they do.

Here's another data point: this 80% of marketshare is reversed when considering profits.