Because we can't outperform Nokia on miniaturization. Even building exactly same thing as Nokia did in N900 would not allow us to go smaller than they did. Rather we would need additional space to implement some things without the very special customized solutions Nokia had at hand, since those sometimes need high initial investment into tools and machinery. Exactly same reason why we use an existing case instead of building our own nicer one. And in the end you want to have more in Neo900, not less - right? /j