So I figured I'd venture into this fray so LITS and his bretheren can skewer me as much as we skewer him on the USMMA forum.
I really don't have any thoughts to add or strong opinions as to whether or not Congressional Nominations as a requirement for entry or the specific processes are good or bad. As I'm pretty new here and I agree understanding where you get your perspective from is important, I'm a 1982 USMMA grad; my son is a USMMA 2012 grad, and I've been an active USMMA alum and Admissions Field Rep for the majority of the thrity years since I graduated.
I think the simpliest most straight forward anser to the original "why" question is an eqally vauge "because it's the law" - actuall "laws" plural as each process has slightly different language in the US Code for USMA, USNA, and USAFA. For USMMA it's the languague in 46 CFR 310 (specifically 46 CFR 310.53).
I would like to add a couple of points to the discussion in response to some of the posts that I think may add a little value to this discussion - not on the why but on the effects that the nomination process has on entering classes, etc that are likely relevant here to some of the posters.
First as LITS" noted (my paraphrase sorry if it's not exact):
"That for places with thousands in a class what about the tine (but not the smallest) USMMA?"
I leave describing how USMA, USAFA, and/or USNA nominations work to experts or at least people more directly familiar with those inistitutions than I. In the case of Kings Point, since USMMA does NOT have at least one spot in each class for each of the 535 nominating authoities, the CFR allocates a number of spots for each state. Each MOC from that state can nominate up to ten candidates for an entering class. Those individuals compete against that subset of candidates with complete application files for that state's spots in the class first. If they are not selected they are then placed into the National Pool and any unused spots are competed for on a National Basis. So for example, let's take my current home state of Virginia. Per the CFR, Virginia has 5 allocated spots in the entering class. VA also has 11 Congerssional Disricts and like every other State two US Senators, so teoretically there could be as many as 130 people competing for those 5 allocated spots at USMMA in the current incoming Class.
In fact given that in recent years VA usually far exceeds the number of residents offered appointments then the allocated five, it's probably safe to say there are likly in excess of 100 highlyqualified candidates with nomninations from VA each year to USMMA. So those five spots are filled very quickly and then the rest Likely 95 - 125 are placed into the Nationl Pool. Given the highly competative nature of seeking an appointment from Virginia, for lots of easy to see reasons - Norfolk, DC, Fort AP Hill, QUantico, etc. it's entirely possible that someone from VA has an easier time getting an appointment out of the National Pool than they do getting an appointmkent for one of "their state's spots". My view is this is generally true for anyone from one of the "Top Five Source States" for any of the SA's requireing nominations. This is not to say anyone from one of the States that seldom uses all their spots has an easy time of it. In ALL cases their are minimums astablished annually to things like Standardized Test Scores, PFT and of course DODMERBB requirements. Everyone entering a class must meet that class' minimums, even if that means there is a nominee from a state with an open appointment spot. So as noted by MedB, everyone at every academy can remain proud and confident that minimum standards are upheld, even when there is a nomnination by an elected official required.
I'll go a step further and diverge for a second and say, all that being true, I for one would have no problem with a son or daughter of a fallen service member recieving a Presidential Appointment to any of the three Academies that have them, and not have that entering PC be subject to any part of this process or minimums. If that happened and they made it through the four years at USMA, USAFA, or USNA, I'm sure they'd be an honor to the service they commissioned into.
Secondly of possible specific interest to Hard-Charger:
I note Hard-Charger indiates their location as VA-11 and apparently their first choice is USNA. Unfortunately for you, I don't know the numbers this year but for the Classes of 2015 and 2016 competition for Congressman Connoley's district's nominations to USNA have been some of the most competative in the nation, as has Competition for nominations from VA-8, VA-1, and VA-10. Further in the case of VA-10 and VA-11 each of those districts has had on the order of 3-5 appointees each year. Last year's prinicipal from VA-11 was a sophmore NROTC student from UVA with a GPA of 3.5+. It is for that reason that in prior years a couple of us in the area worked with a 1996 USMMA graduate who was on then VA-11 Congressman Davis' staff to get him to allow his interviewing board to talk to interviewees for USNA appointments about USMMA. Congressman Davis required each aplicant to designate a first choice and that was the only academy he considered that applicant for that year. He stayed true to his position - he had real considered reasons for it and we respected him for it, however in his last three years in office he allowed the USMMA graduate and the senior USNA graduate on his board to talk to the candaidates for his #5 - 9th alternate for USNA and those who were not going to get consideration/ ranking for a nomination for USNA about their chances for a nomination and appointment to USMMA and what it meant/entailed. Subsequent to that decision, the amount of appointees AND more importantly in my view successful graduates for USMMA coming from VA-11 has gone up markedly. Not specically sure how the curren board handles it but the people on the board have not changed and as I said VA-11 is a very high source of appointees to both USNA and USMMA. For reference and since the interview board for VA-10 is a USMA grad who takes pride in such things, last year VA-10 was the leading source for entering PC to West Point's Cass of 2016. I wish you luck in your quet and don't loose hope regardless of whether your goal is USCGA, USNA, USMA, USAFA or USMMA.
Like I said I'm not trying to enter into the debate as to wether Congressional Nominations are good or bad - especially here on the USCGA forum - just trying to add some additional food for thought on how it works for USMMA as well as how it works in two highly competative districts in Northern VA.