Android as an OS is far less power efficient than iOS, vendors combat this by supplying hardware with larger batteries while often sacrificing the quality of abilities of other components with the applicable space on the PCB / main board layout.
Indeed. Anyway, I hope that Apple release a thicker iPhone, with bigger battery. Maybe we are reaching a maturity level of the market, where they can differentiate the iPhone more.
If you want a thicker phone, why not put a battery case on it?