Once you get used to how EQs work the graphical component isn't really necessary and folks who have been fiddling with this stuff for a while don't need to see the curves. In many ways they can actually be a distraction from what REALLY matters... which of course is the sound.
I used to ask myself the same exact thing and shied away from the less visual EQs but am far more comfortable just twisting knobs without seeing the curves.
Also many non graphical EQ models are intended to respond like their hardware counterparts so those who are used to just turning physical knobs on those devices will feel more at home. The Pultec style EQs are like that and have unique curves/response that are probably impractical to show visually. And really why waste extra design time, screen real estate and graphical processing power displaying graphs when you are dealing with sound?
I still like seeing what's going on in most cases but really, if I have info on the vital params (Gain, BW/Q, Freq*... which is usually displayed in a tooltip anyway but can be learned from product info without) then it's pretty easy to know what is being affected.
That said... I do really like analyzer type displays that show HOW the signal is being affected. I do keep being told to trust my ears though... not numbers, graphs and eyeballs but I still find it interesting to see how signals are affected in real time.
Meh.
*edited because I forgot to add Frequency... oops. Kind of important.