Because it's not Windows...
I'm a Mac user now. I used to use Windows and "tried" Linux for 3 years until I just couldn't take it anymore. Most Windows users just have no where else to go. Seriously, what percentage of Windows "switchers" go to Apple versus Linux. Is there serious marketing for Linux? No. How many times over the past 5 years have we seen articles entitled, "Is Linux finally ready for the desktop? Try distro X now!" Give me a break. I am concerned about Apple's closed policies, but I would rather put up with "Father Jobs" than "Uncle Steve."
Biting the hand that feeds IT
