No one has ever proven or even credibly suggested that Windows or OSX is easier to use than Linux
I'll prove it to you right here, right now.
1: Procedure to use Windows
Go into computer store, buy computer, take it home, turn it on. Wait for it to boot.You are now using Windows.
2: Procedure to use Linux
Go into computer store, buy computer, take it home, turn it on. Find out where to download a Linux distro from. Download enough to do network install. Burn it on a CD. Boot from the CD. Select installation options
Need I continue?
And yes, I do realise that isn't what you meant, but the proof it still valid, and explains why Windows has approximately 100 times as many users as GNU/Linux on the desktop, and will have for the foreseeable future.