[Tomis02]

They don't ask anything because the answer changes nothing. If they get an offer, they'll 99% take it. If they get two competing offers (I'd say this is uncommon unless you're interviewing in a very large job market like SV) they'd most likely know which one they prefer based on their individual criteria (unlikely this would come down to a question asked in an interview).

Second, most people aren't lucky enough to interview for their dream job, they usually have to settle for something else. Consequently, they really have no significant interest in their future industry. Do you blame them?

You want them to fake interest? Sure, they can do that, but does it really help anyone? They applied because they might want to work there, for whatever reason. Why not let them be concerned with how interested they are?