An IGH drivetrain is always heavier, so you never see it on a professional bike. Since the Pros in the Tour de France drive sales all the way down to the 5 year olds, everyday users buy the same bikes that they see on T.V. during the TDF, the Olympics, races, movies like Premium Rush, etc.

Here's a fallacy: the derailleur and the IGH are neck and neck, and the Americans are behind the times.

Not even close. The Derailleur is the superior system for 90% of users, possibly 95% of users. Sure, you could say Joe Schmo Cyclist could technically use an 11-speed Alfine and benefit in his commute, but Joe Schmo isn't gonna drop $1000.