Photoshop makes me feel like a failure. There...I said it. Graphic designers, layout artists, and multi-media artists enjoy all the glory that Photoshop has to offer. For me, it's just not where I want to be.
It's not a right or wrong thing; it's just my personal preference. Ok, for full disclosure and to stop the on-coming bashing from the Photoshop faithful cult: yes, I do use Photoshop every now and then, sometimes for fun and sometimes to fix problems that seem un-fixable.
I want to work in-camera, I want to chase the light and capture the moment. I do not want to layer my way to perfection. There are many valid counterpoints to my view. However, for me, in-camera is where perfection is found.
(see: Fiction or Photography for more info)