Luka is right but just to develop that slightly, you can see it as a way of getting kinetic energy into a static form. Lots of graff touches suggest or imply movment - lines showing wobbles, letters cracking and melting, splashes of paint are about something similar. I think NY pioneer Phase 2 was the person who first used the arrow but I might be wrong. If you think about the flat but mobile surfaces of NY subway cars as the first graffiti canvas, arrows kinda fit.Do you know what the arrow signifies in graffiti?
i remember walking past a Daim piece in Plaistow in the 90s. was pretty mind blowing at the time.Lots of graffiti is about bringing these illusory qualities into the piece - complexity and camoflague added to letters in wildstyles, or 3D and shadow adding depth, size and monumentality, for instance. Some writers have really taken this to the next level, making sculptural complex letter forms - Daim from Hamburg is the guy I really think of here, who kicked this off.
His pieces remind me of Zaha Hadid's architecture.