Expectations.
"I just want a better-looking, better-performing car that I can jump in and drive. Using Windows and going to Linux is like going from driving a car to flying a helicopter."
Correctamundo. The problem comes from those who present that helicopter as a "no learning required!" replacement for a car, and from those who buy a chopper thinking it can be controlled like a car. This includes those who chime in on Windows discussions with "You should switch to Linux!" assertions, and those who attempt the leap because of a near-religious dislike of MS but who neglected to realize the learning curve involved.