It's not about giving your email address to everyone (I wouldn't want that either), but it's about having the friction-free option of doing so. There are a number of game-makers for whom I absolutely want to be emailed when they make something new, because I love their stuff. That doesn't happen on iOS very easily.
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.
