Why does app commercials use only IPhones?

I mean, not everyone uses iPhone.
There are a lot of android users too.

Familiarity. Apple only comes out with 1 phone every year (last year they did 2). There are tons of different android phones, many specific to a particular carrier that come out every year, so the most popular phone model (for now) is an iPhone.

Yeah but they have hte best hardware and best design, and most of the top apps are always on iphones. Even when the same app is on both, I've often seen it where the old version is on android because iphone is where they concentrate their development (makes alot more money on iphones).

Apple's iPhone is much more profitable for app developers. IPhone users buy more paid apps than Android users and spend way more overall on apps. That's why so many apps are on iPhone first-the developers are just following the money. Android users install fewer apps and prefer free apps almost exclusively.