Because when you're new at the whole parenting thing, you can almost swear that every place you go is filled with those who don't like being around children.  It's very nice to hear anything that reminds you that children are "normal".

One time on  plane at the end of the ride a couple people told us our kids were so well-behaved.  What a great mommy-warm-fuzzy that gave me, especially when we were so stressed out trying to travel and keep them entertained so they wouldn't cause problems.  And hey, we didn't even drug them up with benadryl!  ;)