I've tried to switch from Photoshop to Pixelmator, Acorn, Draw It, Gimp and Incscape - but no dice. Photoshop still has the best features for pixel design.
The problem with catering to photographer is probably rather that they already have an awesome, lightweight and modern Photoshop replacement – even one made by Adobe – called Lightroom (and also Aperture by Apple).
There aren't that many really professional photographers out there (i.e. people who do it for a living) but there are masses of hobbyists.
There are plenty of people for whom Photoshop Elements or iPhoto are too simple and for whom Photoshop is overkill. Those people might be tempted to get Pixelmator but both Aperture and Lightroom seem like a much much sweeter deal for them to me.
Lightroom does some excellent workflow management but it also does some (quite complex, actually) photo editing.
Lightroom does do some complex whole-image photo editing, but it still sucks for doing any kind of localized changes. Everyone I know who is serious about photography uses both Lightroom and Photoshop. As mentioned upthread Photoshop can be skipped for the vast majority of photos where you're just cropping, dealing with white balance and doing subtle adjustments, but when you need to make real edits to the contents of the photos, Lightroom doesn't come close to replacing the tools Photoshop has for that.
Original responder was right, Lightroom isn't a drop-in replacement for Photoshop and most people still use both. People who are just doing very light photo editing and could get by without Photoshop could also probably get by without Lightroom and just use Picasa.
I do wish Lightroom added some more of the hardcore content editing features Photoshop has because I'd love to get them into the fully non-destructive editing stack (Lightroom's killer feature), but it likely will never step too much on Photoshop's toes because of Adobe's own version of "the Microsoft tax".
No, Lightroom is obviously no drop in replacement for Photoshop. Photoshop can do different stuff. Conversely, Photoshop is no drop in replacement for Lightroom. Not in a thousand years. Photoshop sucks as a Lightroom replacement, more than Lightroom as a Photoshop replacement.
And you can do localized edits with Lightroom. In the context of Photoshop being fucking expensive I think that’s kinda relevant. Photoshop is that one very specialized tool and you can get by without it.