Because the user can't hover over it and see where the link goes. Because the click handler represents a Javascript program that has to be downloaded. Because i

Because the user can't hover over it and see where the link goes. Because the click handler represents a Javascript program that has to be downloaded. Because it can't be used with Javascript turned off -- which is increasingly necessary these days since ad networks abuse Javascript. But mostly because it's usually unnecessary and smacks of laziness on the developer's part.