Manners and the lack thereof

A thought inspired by a conversation had recently with a clerk at Trader Joe's with whom I'm friendly:

Seriously, can somebody please explain to me what the fucking fascination is with touching the bellies of pregnant women? You people wouldn't want a stranger walking up and slapping you on the ass. Yet otherwise rational, polite people will think nothing of walking up to expectant mothers and giving their swollen stomachs a rub. Is that your stomach? Your baby? If it isn't, don't fucking touch it. You're making the woman very uncomfortable and making yourself look like a thoughtless jackass.