Stern are incapable of making a profitable original theme for two reasons:
1. They don't innovate, and
2. They don't finish the code before they ship.
As Aurich said, pinball machines need something to attract players, and a licence is the easiest way to do it. Another way to get people's attention is to give the game new and interesting features- imagine WOZ as an original theme. The LCD screen, colour changing LEDs, outlane features etc would sell the game. Stern's games have few obvious features that weren't around twenty years ago. Even new Sterns don't have anything that screams "This is a modern, innovative game!".
Then there's code. Play a couple of games of Medieval Madness and you quickly get an understanding of what's going on. Even though the characters and concept are unfamiliar the point of the game quickly becomes obvious- because the code is complete. If some modes didn't work, callouts and animations were missing, scoring was unbalanced etc, location players would soon walk away in confusion, and collectors would be reluctant to buy an incomprehensible game. Hopefully JJP will be smart enough to only ship Pat Lawlor's game when it's actually finished.
