Why do you think this?Sounds like your mind is already made up that they haven't. The more important point though is, Microsoft makes products that run the vast majority of good products in the world. Like I said, they are far more influential in expanding our economy than any of their niche-by-contrast competitors.
The Microsoft vision of the tablet is taking off because of Apple. Chrome and FF show growing market adoption rates.
What has M$ influenced in recent years? I tend to feel that they've been playing catch up in a few areas.