Why are so many people hesitant to update to Windows 10?
People who care about their privacy, security or prefer OSS (Open Source Software) would be hesitant. But for regular user, it'd be application compatibility with W10 and fear the upgrade will break their OS (W7 to W8/W8.1 upgrade was messy)
There are a lot of tools about Privacy Setting available for Windows 10 to disable some "strange" services and functions.
A lot of them can be found on Github, this one for example :
https://github.com/10se1ucgo/DisableWinTracking ; and the good new is you can check the source code because Github.