Of course it isn't. But it's a lot more efficient. I have a hard time buying the concept of paying a designer $500 on a project basis, when I could pay $500 to the best of 30+ submissions I receive.
The internet changed the rules on that business and now I pay $10-$20 an image and an infinitely larger range to choose from. But if you were a photographer making a tidy living in 1993, you may not like that scenario.
Some graphic designers are in the same boat now.