If your child has a medical emergency while away at college ...
If there is a problem with his or her bank account or a financial issue at school ...
In most cases, the medical providers or other institutions will have NO authority to speak to you on your child's behalf unless your child has formally provided you with the authority.
Anticipate the Unanticipated -- encourage your child to execute the basic documents that will allow you to be there for them when they need you.