One reason: People are more comfortable with Windows at first. I use Linux as a mainframe so I am more comfortable with command line but I know how to use it graphically (X-windows).
Have you tried the new Mint with the cinnamon desktop yet? Full point and click GUI that looks, feels, and functions just like Win 7. And it comes boxed with a great bundle of GUI apps including updater, software manager, Synaptic , Etc. The normal average user would almost never have a need to use the command line.
The only time I actually “needed” to use the command line was when I did the slightly more advanced work to build my own VPN server and my VM environment. It’s pretty cool, A windows user can jump right in and fly from right out of the box. They did their homework on this and made it ready for strictly GUI users coming from windows and it very works well.