In most big cities why is paint spilled over the side of the cement walls along side of the freeways.?

When I drive through big cities I always see paint thrown over the cement walls along the freeways. It's not graffitti; It almost looks as though someone just took a bucket of paint and poured it down the side. I've wondered this for many years and can't find any info on this.In most big cities why is paint spilled over the side of the cement walls along side of the freeways.?
Graffiti writing idiots, people who think popping off paint balls at city property is fun. A few years ago the big thing was to full balloons with paint and toss them at other cars on the freeway. Might even be from an 'artist' who has no real talent but decided to share his vision.





what it comes down to is people being disrespectful for no reason than that they did something because they 'wanted too' without taking into account the consequences of their actions and how it can affect others.