For one thing, this level, and these planes, are rather rare. These are truly professional level competitions and people make a living off this- one of the larger competitions, the Tuscan Aerobatic Shootout, has a $80,000 prize and the planes only cost about 8,000, not to mention payed sponsors and the fact that most of the pilots at this level (including George) design planes for the companies (though his "real" job is with Gulfstream).
As for the reasons, I guess its the same reason for some people buying DSLRS when P&S are fine for most people- we know the difference, and these planes perform manuvers that are likely to kill a human pilot in the plane- from g-forces alone.