Because at 18 years old she is an adult. Because at 18 years old she ought to be able to take care of herself, and if she can't, then its because mommy and daddy haven't done their jobs. If parents stopped trying to control every aspect of their children's lives, then maybe 18 year old adults wouldn't need mommy and daddy watching over them.
I wonder if the 18 year old paid for this trip herself? I highly doubt it. If the parents hadn't doled out the money, this would not have happened.
You and I have disagreed in this forum on the expansion of liberty issues, but I cannot agree with you more on the subject stated above.
The greatest gift a parent can give to their children is individualism and self-sufficiency.
Life is full of situations were the risk of injury or death is imminent.
Teach your children to discern and analyze "risk" as correctly as possible.
My deepest and heartfelt empathy for the parents of this missing girl.