What stops someone from designing a blue team technique that is just red team techniques applied to your own product prior to release? I suspect MS does exactly that, but red team productivity varies.
Then, and this is crucial, they not only teach the blue team from their findings - they also rotate out to blue teams, to become the defenders themselves. At the same time, some of the blue team rotates in. Rinse and repeat. The whole point is that you have to understand both sides properly, and continuously work with the teams involved. Otherwise you're nothing more than a consultant.