Remember the “NO WAR” on the Sydney Opera House. SHA removed it.
Graffiti Removal requires certain conditions to be met. It usually takes longer to fix something than to deface or destroy it and this is true for removing graffiti as for other objects.
SHA can remove but also offer solutions to avoid graffiti such as particular agents to coat surfaces which would prevent agents someone from defacing it again. This is a preventative step so that further graffiti removal is never required.