The explanation would be that DMCH see more value in the DMC Brand than they do in the DMC Car. Boosting the brand is easy, producing cars (or even bits for cars) is hard (binnacles, fuel pumps - that don't recall). I would guess the service business is break even or modestly profitable to keep the lights on. The stock of parts is simply not easy to monetize at a reasonable pace. The ease with which they can boost the brand value by (every 3 years or so) announcing a 'new' DeLorean car has got to be addictive. I think we're 1 to 2 years away from another electric, hydrogen fuel cell, fusion powered or something DeLorean announcement - it doesn't really matter because there is no effective way to make it real and they get the brand hit without even trying.
Making an electric DeLorean is really hard - ask me how I know.
Jeff