Its quite interesting watching some of the American Chopper specials, one of which goes through the history of both the Shop and the show. The Teutels weren't the original choice for the show, but a last minute change of mind from the production team bought them in (it was originally meant to follow the restoration of an old bike).
Without the show they wouldn't really be anything and have actually grown with the popularity of the programme as they weren't a large business to start with.
Least American Hotrod follows an established business, but Boyd Coddington is a complete nob, even allowing for the fact that he designed CheZoom one of the best looking custom cars of all time.