Most urban legends have very real origins.
If you scroll to the bottom of the snopes link, you will see that while this particular story is false, there was a very real occurrence just like this that happened to a woman in 1989 where a man kidnapped her after helping her change a flat that he had caused by letting the air out of tire outside a dept store. Unfortunately, she did not survive the attack
The story serves as a good reminder to always be aware of your surroundings.