I totally agree with you. It could be a publicity stunt. However, that is how I feel when looking at it. Whether the artist meant to give the viewer a meaning or not, it is not wrong for that view to feel or see a meaning.
I am not arty in anyway. I try to draw a rabbit for my DD to colour in. No meaning in it except my DD begged me. My DP really loved that picture (it looked more like a dinosaur with big ears than a rabbit) tje reason why is he felt how much I wanted to please my daughter. He felt the picture was drawn with so much love!
To me, it was a crap scribble, to DD it was her favourite animal, to DP it shows my love for dd.
Yes, the above is waffle, a crap example, but my point is, the viewer takes what the viewer wants from any piece of art. I hope I have made my point make sense.
Banksy might have no meaning, but when I see his work I feel an emotion, an emotion I never get looking at one of the greats artwork.