A fire hazard.
Here is a picture of me on the 15th hole at Box Elder GC on the 4th of July. The second picture is a set of clubs that got destroyed in the back of a friends truck. The guy who used to own these clubs threw a cigarette out of the window and it went into the back of the pick up truck. It must have smoldered on a towel ore something. By the time the figured out what was going on flames were 10 feet high. The golf bag that these were in is gone, completely burnt away. I see signs on the highway that read "Cigarettes are a fire hazard". I do believe it is true. Note the burnt golf balls in the picture.