I figure it's a juxtaposition thing, but also graffiti is full of strong planes of flat color, which is a nice counterpoint to the subtle tones and soft textures of the clothes we like.
I've done it once, partially as a shout-out to a friend of mine who had posted a picture of themselves in front of the same graffiti the same day.
I wish I could take more decent pictures, but I'm using a phone, shooting after it's dark out, and have too much clutter to take a decent one. In my last place, I got some great shots.
And surely a tractor is only "urban" by Texas standards.