The success of Android in the mobile market may be one of Google’s biggest accomplishments outside of search, and it may be crucial to the company’s long-term success generally.

But when it comes to ecosystems, Android still lags well behind Apple, which has built the mother of all ecosystems around iOS.

The question for Google: why is that?

There are a number of possible answers. Android is arguably more ‘open‘ than iOS, and it’s the OS for devices from many vendors, meaning Google exerts less control over the end-to-end user experience.

There’s also the fact that Google’s payment mechanism, Google Checkout, generally sucks, making the app purchasing experience less pleasurable, in turn giving developers no reason to focus their efforts away from iOS and the App Store to Android and the Android Market.

But what if there are a more fundamental issues with Android that Google can’t control?

At the Gamelab 2011 conference in Barcelona, one developer chalked it up to Android’s demographic: “Android has potential, but it doesn’t just have fragmentation or billing issues, it’s the demographic too.” In other words, Android users are cheap.

Previous surveys have revealed significant differences between iPhone owners and their Android counterparts, so the notion that that Android fans might be from Mars and Apple fans might be from Venus isn’t entirely new.

But given the penetration Android now has in the mobile market, Apple’s continued lead as the ecosystem of choice should be of concern to Google.

As Michael Schade, whose company Fishlabs builds mobile games, told the audience at Gamelab 2011, “Android is missing a trick; a quality, premium section. Google does not understand that software drives hardware sales“.

The trick, however, may be something that Google can’t create if demographics are a key determinant in whether or not Android users will pay for software.

There’s a lesson here for all businesses, of course: demographics matter. Apple doesn’t need to own the majority of the mobile market to be the most efficient in extracting profit from it.

At the same time, Google can adopt a strategy that results in impressive gains in market share without necessarily tapping the market in the most effective way.

This, of course, doesn’t mean that Apple is beating Google in every analysis (I don’t think it’s always sensible to compare Apples to Googles in mobile), but the differences between the iOS ecosystem and the Android ecosystem should serve as a powerful reminder that who you target is just as important as who you acquire.