[laut]

Macs "just work" for things where Linux doesn't. Photoshop doesn't run natively on Linux, that's alone is enough for many to choose OS X over Linux.

For many people the price difference (if it's there) doesn't matter.

[lightoverhead]

that's the software not the machine. Can pc run photoshop?

[laut]

Mac OS X is the only unix based OS that runs Photoshop natively. Macs are the only way to run Mac OS X except if you make a "hackintosh".

Linux is not as user friendly and integrated with the hardware as Macs. There are certain apps that are only available for Mac. Those are some of the reasons.