Developers could have discounts when the game gets older.
My point is that in some cases Steam or Apple taking 30% is too much, now that Steam has some competition they made some deals with big publisher but this big percentage are to large for some products.
In this debate though many people ignore the creators and feel entitled that the app,game or movie be on his preferred store and using his preferred payment method.
I am sure there are cases where the store works great too.