It's also an easy and accessible way to create something visual and/or express yourself publicly while remaining more or less anonymous.
I think it's very interesting how in some cities, stickers like that are much more common than in others. - there are places where stickers of all sorts are literally everywhere while there are other places where you virtually don't see them at all.
Good point, the anonymous part makes it easy to express yourself in this fashion, and indeed some cities you hardly find stickers anywhere! Tnx for dropping by!