We have places in Zurich where anyone can spray (I'm sure most cities have designated areas like this) but they still come out into the neighborhoods and do it. Its usually in areas with poor refugee/subsidized housing but the people doing the graffiti are local young swiss, making areas where they don't live shittier.
Well yeah, of course they do. Contrary to what what some in this thread are claiming, the modal graffiti isn't self expression or a yearning for freedom. It's tweaking people's noses by altering the property without permission. You can't do that on a designated spray area, so those people have to go into the neighborhoods to get their jollies by pissing people off.