It's not quite even that. Cargo cults aren't just doing what worked before; they're a combination of a valid scientific methodology, and a belief system ("voodoo") which essentially suggests that function follows form, and not vice versa.

Once you believe in voodo, and discount reality to maintain your beliefs, cargo cults make a twisted kind of sense. Then again, once you're willing to discount reality, just about any religion or crazy belief system can make a twisted kind of sense, or at least redefined "sense" until it fits. :-)