One of my favorite magazines, UTNE Reader published an excerpt of an article from imprint that I think addresses this question adequately.
by Caleb Neelon, from imprint
Spray paint dates to about the 1920s, but the history of the spray paint can in its familiar form begins in the early 1960s. By the early 1970s, it was an art medium in the hands of New York kids, who quickly figured out that swapping out the factory nozzle for one from a can of oven cleaner gives a fatter, cleaner line. They also found that nozzles from cans of spray fixative give a narrow, clean line perfect for detailing. By the mid-1990s, enterprising graffiti writers had figured out how to bulk-order these spray tips and were reselling them to other graffiti writers.
Then there were the paints themselves. In the mid-1990s, European spray paint brands such as Belton and Montana really paid attention to graffiti writers, sponsoring projects and even giving star graffiti writers their own signature color of paint. Graffiti writers knew all the nuances of spray paint—coverage, overspray, color intensity, compatibility with other brands—and all of those other details that no weekend warrior out spray-painting his metal deck furniture is ever going to see.
The two main American spray paint companies, Rust-Oleum and Krylon, have always played blind to graffiti. While Belton and Montana each have several hundred colors, Rusto and Krylon have kept their color palettes to about a dozen or two at a time, forcing graffiti writers to shop at out-of-the-way discount stores to stock up on colors available only for a season or two. Since you can’t mix spray paint colors without a lot of fuss, this is annoying. Krylon, a onetime favorite, has been so watered down that it’s simply useless. Along the way, they switched to a “fan” spray tip—the worst for any kind of artistic use—and even worse, made the fan tip more difficult to replace. Graffiti writers pay close attention to nozzle quality and its ability to accommodate a variety of nozzles. Krylon simply removed itself from the artistic-use market with this one move.
American graffiti writers are fiercely loyal to Rust-Oleum, however. Rusto is legendary as the thickest and most durable of all spray paints. It’s not for finesse: The thickness of the stuff precludes detail work, but there’s nothing that’ll last like it. Unfortunately, Rust-Oleum is busily making a switch to a “female” cap—one where the little post between nozzle and can is connected to the can, not the nozzle. It’s a small detail, but they wouldn’t have done it if they had listened to the people who know their products best.
European spray paints took a while to arrive in U.S. markets, but they’re here now and easy to find. American graffiti writers who would go through hundreds of cans of Rusto in a year are now using Belton, Montana, and a new arrival, Ironlak. These European spray paints can cost twice as much as their American counterparts, but artists are artists and they’ll pay the price to make their work.