Re: Time to go sell real estate?
As you say, HR is looking for any kind of filter to screen out as many of the applications as possible. They can't carefully scrutinize 100 applications for a position, and they can't pass on to the hiring manager 50 of those applicants who might be qualified.
So consider the consequences of either type of error in their selection, false positives or false negatives. If they pass on a candidate who is unqualified, or even just one who the hiring manager doesn't like, they get yelled at "Why are you sending me these people? You're wasting my time! You're supposed to be screening these duds out!". Whereas they could reject any number of perfect candidates, and the hiring manager won't say anything, because he/she has no idea that happened. So there is a huge bias towards tossing applications out, even if there is no good reason to.