If you dive into the graffiti scene a bit you will start to appreciate all those graffitis. The story behind some of them is super interesting. There is a lot of "competition", "collaboration", and group dynamics involved. It is truly fascinating. I was living in Cologne (Ehrenfeld) for a while in a place with awesome graffiti and every weekend there were people taking pictures "collecting" and documenting the graffiti.
Edit: Not "all of those" but "many of those"