Street art can be found in many cities. I have seen them in several major cities in the US, UK, Brazil (these are very colourful. especially in Rio & Sao Paolo), Argentina, Chile, Prague, Australia, Germany etc
As long as these are not eyesores, it's alright. Sometimes there are beautiful artwork even on the pavements.
But in SL when something starts it becomes a craze. Once there was a time when people started growing Manioc, some said we should even plant them in the railway track.

There are some other things that makes me really wonder. One example is why the younger generation run hysterically behind a bus with fancy lights and musical horns. Are we getting dumber from one generation to the next? I can better understand why the ancient cultures worshipped the Sun, than explain why another generation in 2019 running behind a bus.
It's a good thing to make cities cleaner and look nice. I have no issues with it as long as it's done with a limit - unlike that manioc story.
Of course it does not contribute to the economy of the town, unless there are visitors coming in to view these from outside areas.