And or course, there is always the ability to just write an HTML 5 app, point people to a URL, and have them add it to their home screen. All without ever touching Apple tools or a Mac, and without having to go through Apple's approval process and the store. Apple will even add it to their list of web apps if you submit it to them. http://www.apple.com/webapps/

Developers are the ones choosing to support the iPhone and it's "closed" environment, so for most of them, it must be worth it.