B-schools based in the US use a unique self-selecting mechanism to filter out applicants who might be a bad fit for a management job. This they achieve by making the application process more complicated, but in a way that the kind of people they hope to attract find it simple.
Let me explain. Like most other graduate programs in the US, B-schools also require applicants to get a set of letters of recommendation. Unlike other programs, though, these are not simple letters of recommendation. Rather than the recommender simply writing out one essay where he/she extols the virtue of the candidate he/she is recommending and requests the university to grant admission, here he/sh has to answer a bunch of questions that the university is asking for. These questions might range from the mundane sounding (I’m told there’s a catch, though) “How do you know the applicant?” to some high-sounding stuff like “What is your opinion of the leadership qualities of the applicant? How can that be improved?”. World limit for all questions put together comes to 1500 words.
So now, if someone comes to you asking for a recommendation, unless you are really invested in their careers you will not want to put the enthu of putting so much effort. If you like the candidate, you might be willing to put in some time into it, but you are likely to wholeheartedly produce four good essays for each school the applicant is applying (note that no two schools ask the same question) only if you feel really invested in the applicant’s career, the probability of which is really low.
By having such a complicated system of soliciting recommendations, the schools ensure that all candidates fall into one of two categories. Either they should have done so well in one of their jobs that their boss or client feels invested enough to spend a few hours of their time writing recommendations, or they should have the necessary people management skills to go to bosses and clients and professors to get them to write the recommendations. Of course, irrespective of how good your people management skills are , it is unlikely to get someone to spend so many hours on your recommendation letters. Still, the minimum you require is to convince them that you will write the recommendation yourself and they should rubber stamp it. No big deal, that.
This way, all applicants to US B-schools are people who have a knack of getting things done. The age at which application happens (mid to late twenties) also minimizes parental participation in the effort. Apart from the self-selection and filtration, the amount of time and effort required for application also helps weed out frivolous candidates (remember those that “wrote CAT just as a backup”?).