many belief if they are not a graphics designer they can design as a graphics designer. does that mean they know all it takes to be a graphics designer?
There are a lot of concepts to learn, not are only creativity and aestethics, also we have to know a lot of concepts to solve visual communication problems: visual forces, complementary colors, kerning, tracking, typography, contrast, hue, the meaning behind a color, substractive and aditive models,cultural factors, the trends,history,fight with the printer 'cause the color changes :P, do an approach in minutes... for this reason the graphic design is, more than a carreer, a lifestyle =D
There are lot more concepts available to learn and to work with. But it requires a lot of patience to learn and as the new technologies are coming, it will become much easier.