My problems with GIMP were the CMYK stuff and a few terminology issues. I really love the GIMP interface, and I'm not the only person who finds the Photoshop interface awful.
I think that people just hate to have to learn anything new, and are willing to pay rents for the rest of their lives to fend that moment away where they might have to spend up to a week or more working in something that they're unfamiliar with. It's a bit like the fortune web developers pay to not have to figure out unix, or Apache.
Or like using a guitar tuner to tune each string separately. Maybe I'm just an angry guy:)