I'm pretty sure that in the US that question is illegal to ask an interviewee. It might have been beneficial in your case, but is still totally illegal because it is one of the ways the sexual discrimination in hiring propagates.
> I'm pretty sure that in the US that question is illegal to ask an interviewee.
It is not. (Like most questions that people think are illegal to ask in interviews, its merely ill-advised to ask because it asks specifically about something on which it is illegal to discriminate in hiring, and asking about it in an interview is -- on its own, weak, but still -- potential evidence of its use in a hiring decision.)
(Cargo cult HR helps perpetuate the myth that these things are illegal to ask.)
Okay, it might not necessarily be illegal in the general case, but in the specific case described by the OP, asking that question, getting an answer, and then saying "See you later <eom>" makes it clear that that was discrimination in the hiring process based on family responsibilities, no?
