If I want to go in a straight line then yes, I agree lower bb would be better.
As for Lance and co, sure they are good, but so was Giles Coust and Vince Hermance when they rode level bb frames (thought the best geo at the time). I am pretty sure a level bb frame would hold them back for a lot of stuff now, I predict dirt and street frames will eventually get higher/shorter backends as riders finally realize there is a reason why bmxs are like that.
(and yes I do realize I am comparing two different sports, but the point remains)
While I am on about bmxs, lets look at the geos of the different types.
Race bmxs need to be stable at speed and in the air, they have no need for spins so their frames are usually longer in wheelbase and chainstays as well as a lower bb.
Dirt frames get slightly shorter for easier spins, but are still a bit longer to help stay stable when being a trailboss.
park and street frames get shorter wheelbases, shorter chainstays and high bbs to help with spins, they don't usually go as fast so don't need the extra stability.
Flatland, super short, super high, no need for stability when you only travel in circles.
The NS frames are a step in the right direction, but most people still use frames with geo also suitable for 4X (EG, Race bmx above). Perhaps people arn't ready for more radical geo much like trials didn't like high bbs when thy first came out, but once people realize the benefits I think it will be popular.