I don't know... I've got 2 "old school" hardtail, long wheelbase mountain bikes. They're comfy. They're stable. They're burly.

My guess is that 99% of the people that ride bikes are not "mountain bikers" or "racers." They're people that enjoy riding their bikes. Some commute, some run to the grocery store, some just ride for the heck of it. Things that are perfectly suited for a comfortable, stable bike. That's a whole lot of applications for an "obsolete" bike.