Yes, app stores is where most people get their applications for their smartphones today. While this is convenient, simple and offers a way to earn money I'd argue it's not the 'natural' state of things. I'd never buy a PC, notebook, netbook or any other device where I can only download programs from a single store that is controled by a single entity with its own agenda. So why should I limit myself to that for a mobile device (think smartphone, tablet, etc.)?
This became quite apparent from a technial point of view to me when I recently tried to download something from an app store and couldn't due to some strange error that persisted for quiet a while. Well, at least I could download my most favorite apps (web browser and email client) from the web pages of the developers and thus bypass the store and the problem. A single point of failure, always a bad thing.