Why Doesnt Notch Remove Herobrine from Minecraft?

This has puzzled me for sometime now, in each of Minecraft's Major updates e.g 1.3 or 1.5, Notch always states at the end of the change log: -Removed Herobrine. I think it is because he does not want to or he wants to make Herobrine mysterious and make us think he has removed Herobrine. Maybe he wants to scare the crap out of us when we see him. I have never actually seen Herobrine in any version, but I know of people who have. 

Here is a person who found Herobrine.

Hope you enjoy this, Let me know what your take is.