Even if people tell you that a graphics card is only more suited to heavy hardcore gaming, the sort of games like 'Call of Duty' and such and so on, and that photo editing software like Photoshop don't need to rely on graphics card, and can manage on processor and memory alone, it would still be good idea to get one anyway. You could benefit with the graphics card offering to support more than one monitor, such as that you could be editing your photos on one screen, and have the second screen for any other work or Internet or watching videos or whatever you like.
I usually often do some typing in a word processor, highlight the text, copy it, switch windows for the graphic design software (in my case CorelDraw) and paste. But it would help a lot if I have two screens so I don't have to keep using Alt+Tab or going to the task bar to switch windows all the time.
You could also still use a graphics card in case you one day decided to go for 3D work.
You don't have to, but I would find it helpful anyway, I'm still learning about graphics cards as I'm planning on buying one for my project to build my own computer, and as far as I can tell, those cards often kind of helps to take over some of the display workload from the CPU and RAM if the going gets too tough for them.