I saw a video where the artist rode her bike around Portland looking at all of the wiped graffiti. She thought the people doing the paint overs were actually expressing themselves as artists because it was usually beautifully done in different colors. She was also making fun of the process. So much amazing art wiped just because it's not selling products. Banksy being the exception.
Edit: Banksy's self-destructing art when it was sold: https://www.youtube.com/watch?v=iiO_1XRnMt4&t=59s