Ballmer is a bean counter. To my knowledge, there has never been a successful software company headed by a bean counter. Bean counters do not understand the 'creative' essence involved in programming. All the gray areas. Bean counters are all about black and white, with plans that cannot be altered. There is no such thing as a surprise to the well endoctrinated bean counter.
Most of what makes a good bean counter is counter-productive in a software design business.
So he sticks to marketing. It is something that makes sense to him. It also makes him look foolish to the technical community.
Gates ego will never allow him to admit he made a mistake. At least publicly anyway,