Those who indulge in vandalism or illegal graffiti are largely young people who under-achieve at school. Add in boredom, alienation, family and community breakdown, lack of leisure opportunities and youth unemployment ... and on and on. Complex root cause. Not the brightest bulbs at the lamp factory. I mean, we did some goofy things in high school and university*, but never would consider causing permanent damage to something others enjoy.
*I recall landing in front the university council with a few others for hanging a sign made from a bedsheet on campus as parents were driving in thanking them for dropping off their daughters ... well, the exact wording I will not repeat here, but it was adults with an adult audience and I'm sure I'll pay for it again when I drop off my future kids.