This is my biggest complaint about my smoking co-workers. What they do on their break is their business, but sheesh, what a disgusting mess they leave by the entranceway. I don't throw my garbage on the company lawn, why must they?
Maybe if your company provided outdoor ashtrays, there wouldn't be a mess.
They don't have this problem where I work. Could it be due to the designated smoking rooms with ashtrays by any chance?