Why though?

Does it stem from unwillingness to learn something new, or does photoshop do something differently that Gimp cannot?

Last time I used photoshop I was in college and found it to be meh. Do not know how long away it has come since then.

I have heard this argument from a lot of people, but i just don't get it.

I've been able to use it professionally for over a decade with no issues. The latest 3.0 upgrade was pretty sweet too.