Because Sharp has chosen to take a different path than Apple. I think Sharp is eager to preserve the quality of the applications that are developed on their platform. Thus, one might call it a closed architecture, and others might call it selective instead. A very good question. The most important thing I would tell anybody is that it takes a commitment to long-term development.
Technologies change and new platforms emerge onto the market place.
We have seen a lot of people come and go who have tried to develop a single application. You really have to be committed to it. Sharp is so customer focused. Sharp could come out with a unit that would make our current application obsolete. Sharp is interested in giving their target customer what they need, so developers have to be ready to spend the extra time to rework an application.