If you think the only difference between rpm and deb is the packaging format then you've completely missed the point. What makes Debian great is not its packaging format (which is just an ar file) but the Debian packaging policy.
The policy that ensures that files end up in predictable places. The policy that ensures your package will not be broken randomly by other installed packages. The policy that ensures the each package can be reliably rebuilt by anybody on any system. That they don't clash in user names, program names, port numbers, etc...
It's the policy that allows you to take a system and install tens of thousands of packages and have them ALL work. Simultaneously.
Distributing files was a solved problem long ago (.tar.gz). Today, a .deb is a sign that someone put effort into it. A mark of quality. Changing deb files to look like rpms would be technically feasible but pointless without everyone following the same policy. Rpms have their own policy and unless they align, nothing will go anywhere.
If you don't care about policy, use alien to convert the packages.