Cydia is more than just a frontend for http/wget. It is a port of Debian APT. Iirc saurik did make some passing notes about possibly bringing APT to Android. However, from the lack of any implementation thus far, I can only surmise that he has either lost interest, doesn't feel Android needs an APT-based repository, or some mix of both.
You have to understand the main reason why Cydia is a very popular platform for iPhone. iPhone natively does not allow any outside app installation. Thus, Cydia provided a very good central repository for apps outside of Apple's app store system. Android, OTOH, was built from the ground up permitting the user to install apps from any source. Thus, there was never a burgeoning need to have a Cydia clone made because anyone could install apps from their own http server, from adb, from a sdcard, from a third party market.