I beleive the speculation is that Apple have avoided opening up the iPhone so they will not have to support legacy apps when they switch to the intel platform.
I think it is simpler than that. Apple rushed the iPhone out the door. Sure thay has a bunch on interesting tech, but not as a choerent product. They had to pull developers off Leopard to hit their launch date - and even then there appear to be issues with ill-conceived features and functionality (some of which got fixed in the update). The simple answer to the question of why there is no dev kit for the iPhone/iTouch platform (aside from AJAX web apps)? Apple just didn't have the time to mess with anything but the bare essentials.
It will be Bootcamp all over again. Lots of third party hacking about, then suddenly Bam! iPhone Dev Kit at 2008 (or 2009) dev con.
Apple products "Just work". Problem is the new iPhone/iPod Touch platform "Only just works". It needs time to bed in and have Apple polish it some more.