It's all great until your stuff gets destroyed because someone thinks it's better a different way. And when the graffiti is truly spectacular you can find some consolation in the result, maybe truly appreciate it. But that's not the case 99.99% of the time. Most graffiti is just trash, some rando spraying their name somewhere. Takes 10 seconds and 0 talent. It causes extra expense for people or the city to clean up, or it stays there as an eye sore for everyone.