Probably for the same reason other systems don't even allow you to run things as root. Warranty, support and liability.

If Nokia had simply used the standard debian way, people would have sooner or later get "infected" by arbitrary packages replacing "system" packages. So HAM has some kind of protection for this.

Obviously, given the current state of affairs concerning both Maemo and the people using Maemo I think it's about time we drop this nonsense and get rid of HAM and FAM (or at least of their arbitrary restrictions) and use only apt/dpkg. Heck, even apt-get is arbitrarily castrated (so as to prevent installing OVI stuff.. does OVI still exist?).

What we also need is fixing the dependencies of many packages. This will prevent breaking stuff with or without --auto-remove (auto-remove should NOT break stuff unless the dependencies are broken).