Wikipedia has a category called "Graffiti and unauthorized signage", which strikes me as very funny, because it presents a POV that 1. the most salient feature of street art is that it is not authorized and 2. it all amounts to signage, like an awning on a deli

It just seems very...stick up the ass...about it.

If you draw bubble letters in a notepad, it's art, but if you take that image and paint it on a brick wall it becomes (harumpf) an unauthorized sign.

Idk it's just such a peculiar worldview, it's like a crystallization of thinking about things purely in terms of whether they are legal, and/or make money and/or spread a particular message. And it's applied so broadly that a Kick me sign taped to someone's back is equivalent to an abstract mural