I hated that show, yet everyone I know loves it. Of course, I didn't watch more than an episode or two.

Nickelodeon canceled it for one of two reasons:

A) Because it was very dark and different from the run of the mill crap they sell themselves on, thus not bringing in as much as something along the lines of Spongebob would.

or

B) Because Nickelodeon has vowed to themselves that complete crap and ONLY complete crap can be aired on their network during daytime hours now.