Or rather, sure: they do on the business side. An app store is a commodity. Samsung has one. If enough users use only Samsung phones then Samsung can sell the apps directly. But that's only true insofar as Samsung phones are clearly better. And right now that property is a combination of some nice hardware and... Google's innovation in Android. Take the latter away and you basically have AOSP on nice hardware, and that's not going to sell many phones.
Long term I think this will settle out as phones and mobile OSes become less differentiated. Samsung too (and Apple, for that matter) will succumb to the inevitable: there really isn't a whole lot of money to be made in selling latte-priced apps in an increasingly competitive market.
http://www.theverge.com/2013/2/25/4026848/bada-and-tizen-to-...