Not sure where you're getting 15% from: the vast majority of articles I read have Apple's app stores generating far more revenue than the competition's. So yes

Not sure where you're getting 15% from: the vast majority of articles I read have Apple's app stores generating far more revenue than the competition's. So yes, I believe Apple is probably perfectly happy (in an upper-echelon corporate strategy sense) sitting on their cash cow as opposed to fighting it out for less profitable market share.