Thank you for making my point: there are in fact hiring managers who think like you type.

Now, add to that this fun bit: when a woman has a kid and stays home with them, she winds up with a gap on her resume. During a normal career, an unexplained gap is an obvious topic of conversaton in an interview. Women with kids can't effectively avoid disclosing that they have children, even though it's technically unlawful to ask the question directly.