"Laws strickly enforced"

Today as I was driving down the road I was struck by a sign below the speed limit sign which stated "strickly enforced."  I found it interesting that there was a need to make this statement to remind those of us on the road that the laws are enforced, and therefore we should follow them.  Shouldn't the law's existance simply speak for itself in that it is a law and it should be followed.  Why must we be threatened with "enforcement" before we will adhere to the laws laid before us?  How does this coorelate to the commandments and teachings of the Catholic Church?  Do we follow the commandments before us because we know them and we know they should be followed, or do we follow them only when we fear the threat of "enforcement?"