Legacy
In the end, no matter what happens, Banksy and his artwork have surely reached legendary status around the world. They are valuable pieces of work but share a lot of valuable messages that are done in a very clever way. It is more than what we can say for a lot of other things we see around us today.
His hidden identity goes against the norms of today where everyone wants to be famous and a celebrity. He could easily reveal to the world just who is, but he chooses not to. Not just to protect his private life, but to send out a strong message that he is in it for the art and nothing else.