There's definitely a focus on feedback from coders in most open-source apps - and that makes sense as well, although I'm sure it can be frustrating.
As a coder, I've found that it can be very hard to communicate with non-coders about coding or design issues - and this seems to be mostly a case of one of us not understanding the domain-specific language of the other.
At Adobe, I'm willing to bet that a lot of the design and goals for abilities are found and decided by people who aren't programmers at all - or who are, but are also very involved with professional-style photo-editing, and that by the time it hits the people coding, the decisions that don't have to do with implementation have been made. (This is only one possibility, but I'm sure there's some sort of "translation" layer there)
I would be somewhat surprised (but not to a large degree) if the GIMP camp wouldn't be open to suggestions from professionals in the field, but communication might be difficult as the users don't understand the coders language, and the coders often don't understand the users language. People in both camps are rare - and in the case of the GIMP (and a lot of OSS), people in both camps are really comfortable using (for instance) interfaces that aren't really up to par, or having the ability to create the extra features they need instead of having those features by default.
There's also the problem with some groups of developers ending up being elitist cocks towards users that want there input heard (There are also elitist cock users, but whatever). There's not much that can be done about that, but it seems to be a decreasing trend as (high-level) programming becomes more mainstream.
Don't get me wrong, GIMP is not a bad program. I particularly appreciate it being scriptable in Python, which is my day-to-day bread-and-butter language. But for professional (i.e. stuff that people pay money for) photography targetting print output, it's nowhere near Photoshop - and it's very clear that the authors of GIMP don't understand why. At Adobe, they listen to photographers and designers and the programmers understand that they're not the domain experts. In the GIMP camp they suffer from the same problem as most open-source projects; people who can't code aren't really taken seriously.