It could also be a culture question. I worked on a trading floor and we'd make "markets" on when lunch would arrive, the cost of an airline ticket, the number of times I would injure myself in a week, etc. While there are more precise ways to ascertain a potential hire's arithmetic and estimation skills, this is more fun (especially since the interviewee's answer would usually kick off a round of bets being placed by the team on what they thought the answer was - this had the added benefit of giving us a relevant distribution to test the candidate's answer against).
It also drew out people who may not be a fit for our desk's culture of camaraderie where answers to banter along the lines of "that's personal" or "that's not relevant to my job description" would be awkward at best.
Additionally, I have heard from consulting buddies (the heathens!) that it's can good way to see how well a candidate can bullshit on little to no relevant data.
In any case, I don't think it's empirically valid to conclude someone a moron for asking brain teasers in interviews. I never asked them whereas many people much smarter than me did.
It also drew out people who may not be a fit for our desk's culture of camaraderie where answers to banter along the lines of "that's personal" or "that's not relevant to my job description" would be awkward at best.
Additionally, I have heard from consulting buddies (the heathens!) that it's can good way to see how well a candidate can bullshit on little to no relevant data.
In any case, I don't think it's empirically valid to conclude someone a moron for asking brain teasers in interviews. I never asked them whereas many people much smarter than me did.