As has been said before in various forms, a lie can make it around the world before the truth has pulled on its boots. That has only gotten worse in the age of the internet. The truth can hardly get a sock on, never mind boots.
And by the time truth has finally made it to the scene, a lie might have set up shop and dug itself in, harder to get rid of than ever. That's why we do this — to help finally scrub away some of the internet's most stubborn grime.