Because--and this is what gets me--her pediatrician told her the same thing, but she and her husband wanted to talk to a nurse, because nurses really know what's going on.
(Never mind that I know next to zilch about pediatrics, and that heat-rash is pretty easy to diagnose.)
It gives you the warm fuzzies.
(Plus, I got to play with a baby for a few minutes which, if you are a fan of babies for a few minutes at a time, as I am, is not a bad thing.)