Lets be honest here , the biggest reason by far that Win 10 is on more computers is because it's free.
When i found out that turning off all the features that invade privacy doesn't do much and Microsoft has the ability to completely control your computer (as it stipulates in all the fine print for Windows 10), i personally think this new OS would be no more popular than 8 .
Microsoft's vision clearly shows they wanted a multi platform OS which is what many didn't like about 8 but many peoples biggest beef is the lack of control over their privacy without specific registry hacks , thats what it will take (according to those in the know) to make Windows 10 less intrusion based .
When something is offered for free it's pretty much a given it will be successful , the overwhelming majority will take advantage of a free OS . I still don't think the majority of people know just how much control Microsoft has and what is happening behind the scenes though and thats good for them.
I like Win 10 , just wish it wasn't so overloaded and purposely deceitful .
Check out how much control they have and this is a short list: