The bottom line is that developers like tried and true technologies and won’t move away from them unless customers demand it.  Those same customers are largely pulling to keep XP around, so obviously they haven’t seen the value in those new technologies yet.  If customers don't have the need for new features that only Vista can supply then they are unlikely to make demands from their software suppliers.  This gives software developers extra time to determine if they’ll make the jump, or if they’ll wait for the next big thing.