That's not quite correct, Windows 10 has been adopted faster than 7 or 8 because it's one statistic Microsoft has been shouting from the rooftops since release. But we all know the precise reason for this and it's the free upgrades that have caused it, whether you choose to upgrade or are coerced.
Every version of Windows has been force fed onto users by some degree because it's what you get when you buy a new computer, like it or not. Most Win 7 users didn't run out and buy the os, it came with their computer and they just happen to like it because it's a good os.
It's interesting to see that Win 10's share only went up by around 1% considering they started rolling out the recommended upgrade at the beginning of Feb.