I think the issue is more than that.  On the Evian site there is a
breakdown of how much water a person needs to take in each day.  For an
infant it's written 100 cc/kilo.  That means a baby who weighs 4 kilo/8.8
lbs needs two cups/day!  Can you imagine what horrible consequences could
result if a mother decided to give her baby JUST water for those 400 cc.
each day?  Poor weight gain, right?  then the doctor would tell her the
baby isn't gaining well and her Bm isn't good enough,etctetc.  Would he ask
if she was giving supplements? I doubt it.  besides, most women don't
consider water a supplement.. the hospitals certainly don't seem to
categorize glucose water as a supplement.

This chart also gives the impression that there is no H2O in breastmilk.

Nofia