I think you are being too specific in your interpretation of urban legends Rhom. They do stretch beyond babysitter stories and psychotic killers.
The strict definition is
a folkloric and often sensational tale about modern life that is repeated in the media and by other means, making it more believable to some.
This covers any number of topics and there are urban legends about everything from coke to disney and the vast majority have no moral behind them at all, or if they do it is unintentional
I do agree with you though that they do strongly reflect the society in ewhich they are told.
In a recent Psychology class we learnt about an experiment by a guy called Bartlett who told a group of Englsih people a native American story called 'the war of the ghost' then later asked them to recall it. He found they changed the story to reflect their own everyday ives e.g. replacing canoe with boat, bow and arrow with gun.
I believe the same thing happens with urban legends and some details are lost, changed or added in the passing on, even between people in the same culture. Hence the many versions of myths which are evident even on this site
In closing I would like to thank you for finally posting a true discusional thread on here, rather than just a story for people to ooh and ahh at in one sentence replies. Cheers