I don't think the reason that ads are allowed is because people prefer them. The reason is that whoever puts an ad does so on their own property. You don't put

I don't think the reason that ads are allowed is because people prefer them. The reason is that whoever puts an ad does so on their own property. You don't put an ad on someone else's wall against their will. Graffiti, on the other hand, is usually done without authorization from the owner of the wall or facade being graffitied.