Billboards

I always laugh when I see billboards on the highway.  It's not like we can stop what we are doing and right down the phone number or directions to the nearest Motel 6.  Why do they even have billboards?  I know the obvious answer, but what is really the point?  They are distracting, hardly ever informative, and usually an eye sore.  Who cares?  Well I guess I do, but I'm not quite sure why.