Renegade> Well, it's true for rather simple projects. If your project is simple, you'll do better with a simple tool (ie a mobile app). I can doodle on my ipad and make some nice stuff, but for serious work i'll switch to Photoshop, Manga Studio etc.
-ak_
The telling thing there is that you mentioned Photoshop. (I use it too and love it.)
It really puts people like you and I out of the picture.

We don't fit into the normal user demographic at that point.
I think that it suits what a lot of people want to do though. Photoshop makes you a god, but few people have divine aspirations. Most of what I do is relatively simple, but impossible on a mobile. I think most people have pretty simple needs.
The only thing that I really do much of on my mobile is read news and post it to Facebook every now and then. The form factor, for me, is simply too limiting and frustrating to use. But, it suits a lot of people.
Those like us out there will continue to crave the raw power you get on the desktop. Different strokes I suppose.
I think simplifying things makes functionality more accessible, which in turn is kind of like what you mentioned with "it's actually what you can do with them that is exciting." Most people can't do ANYTHING in Photoshop, but a doodle program is accessible.
Oh -- off topic, but have you seen any of those MS Paint videos where someone creates some wicked amazing art?