I probably talk about baby poop way too much, but I challenge any parent to claim that they don't find their own child's bowel movements a source of endless fascination. Hell, I've heard educated and well-dressed couples discussing it matter-of-factly over dinner at a nice restaurant.
When you have children, poo becomes such a routine part of your day that it ceases to be disgusting (although there are always extreme cases). In fact, for most parents, the load in their child's diaper acts as a daily print out of their overall health and wellbeing. The fascination stems from the reassurance that at a glance you can mostly tell if that they're feeling well, eating at least a few vegetables, and staying hydrated. Reports are relayed to your spouse with all the detail an accuracy of a medical exam. If the child is unwell, one of the first questions is "how is her poo?"
For a while it made me wonder how parents of older children keep track of this stuff, but then I remembered that older children can generally string sentences together to more or less accurately relay how they feel. And the fact that their parents don't try to substantiate those statements by poking around in the toilet (ewwww), reassures me that this fascination with the contents of my children' diapers will one day wane, and I will be able to return to polite society. Maybe.