Why not? Every app page has a link to the developer's site, and the developer's site can offer a way to subscribe to some sort of newsletter. And games often provide links in the game itself to view information about the game developer.

Edit: I recognize that it's not particularly common for developers to try and encourage users to sign up for some sort of marketing. But I think that's just because developers haven't really considered it to be an acceptable thing to ask users of their games for, rather than any actual difficulty in doing so.