Why the ash tray?

Thirteen years ago I was able to kick the smoking habit, which by the way is the worst habit ever created by man. As a reformed smoker, I am thrilled to see all of the smoking bans being passed. Especially in restaurants and public places. Recently while strolling through a public place, I noticed an ash tray near by. There was a sign posted on the ash tray that stated “smoking in public places is prohibited by law” My curious little mind couldn’t help but wonder, why didn’t they just remove the ash tray? whatzupwithat?