Noone is using windows because it is cool and hip and i doubt microsoft advertises windows. People use windows because they work and do what they want. Maybe they could use ubuntu, but why would they do that? What does ubuntu offer that windows dont?
I'll tell you why they(including me) dont use linux, because maybe their wifi wont work(or they will have to compile the universe to make it work) or their favourite app or game wont work. And even if you could make a piece of hardware or software work in linux, the performance might be inferior because it will be using generic drivers, instead of the proprietary windows only drivers that the manufacturer has made.
Ultimately, people dont care about open source or privacy enough, to sacrifice their convenience.