Graffiti tags are relevant to someone other than the "tagger" as well.

"Tags can contain subtle and sometimes cryptic messages, and may incorporate the artist's crew initials or other letters."[1]

Just because you and I don't get it, doesn't mean it's content free.

I'm not defending tagging, I'm just decrying most advertising as being equally bad, or worse.

[1]: https://en.wikipedia.org/wiki/Graffiti#Tagging