The "Benefit or Need" to more than 1 nomination that you refer to, is actually very logical and natural. Although, a person who might not understand what and how nominations work, might think it would be odd to have or need more than 1. Here it is, in a nut-shell.
1. An average academy, say the air force academy, will have approximately 10,000 initial applicants or prospects. But there is only room for approximately 1300-1400 cadets per year.
2. The various military academies like air force, west point, etc... are "FEDERALLY FUNDED" by tax payer dollars. Therefor, the "STATES" have the "RIGHT" to be equally represented to the best of the academy's ability, when selecting the 1300-1400 appointees for that year. (Yes, that means that a selectee from one state, could possibly have a lower overall package score than a non-selectee from a different state, but each state has the "RIGHT" to be equally represented. It's not perfect, but it IS the most fairest).
3. Each senator/representative gives 10 nominations "PER ACADEMY THAT REQUIRES ONE" each year. So, with 453 representative, and 100 senators, that's 5530 nominations. Then there are a few more nominations separate from these, that are afforded as a "BENEFIT". E.g. Military members, in HONOR of their service, are authorized that their child be given a nomination from the president for the military academy.
4. Even with these 6000+ Nominations total, that's still more than the academies can admit. They can only admit 1300-1400 appointees.
5. There is no way that the senators, representatives, president, vice-president, ROTC, and other nominating officials can tell who is the "MOST QUALIFIED" applicant. These individuals don't have the time, nor the knowledge of the overall "Whole Person" attributes that the academies are looking for and are scoring for. Therefor; the academy has these nominators provide a SLATE of 10 nominations (For senators and representatives), and the academy is generally allowed to "CHOOSE" which person on that list of 10, should receive an appointment. Same for the presidential and so on. Once one from each list of senators and representatives have been chosen, and the others for president, vp, etc... are chosen, there will be about 500 additional slots available.
6. These remaining slots are chosen by taking ALL the remaining nominees from each of those senator's and representative's lists of 10, who didn't receive that initial appointment, and they are placed in a pool for the academy to choose the remaining 500+/- from.
7. (Now, the reason for needing multiple nominations). By federal law; because each state is authorized the RIGHT to be equally represented, that means that each senator and representative, can ONLY have 5 cadets charged to their slot, at the academy at any one time. So, you might have a representative's nomination, but another individual on that list of 10 from the same representative, may have been chosen for that slot above you. Well, you missed out. HOWEVER, if you also have a nomination from the senator, and they have slots available at the academy, you might be the highest ranking on the senator's list, and you could be chosen for an appointment off of that list.
8. Basically, a little more than HALF of each year's class, is filled by nominees representing either their state, congressional district, military parents, rotc, active duty, reservists, etc... You have a much better chance (1 in 10) competing with someone just in your district or state, then you do if you go into the general pool. By the time the general pool is chosen from, there can be approximately 5000+ people in this general pool. ALL with a nomination, and ALL competing against EACH OTHER for the remaining 500+ slots. Yes, the odds "SEEM" to be the same as competing for the 1 in 10, at your district/state, but at the local level, if you have more than one nomination, you're competing against others generally with the same educational, social, economic, etc... background; compared to others from different backgrounds.
Anyway, that is about the MOST OVER SIMPLIFIED way to explain it. "Please, no one argue with me about "DETAILS". I was speaking VERY GENERAL to explain why it wasn't actually odd, and why there was some reasoning behind trying to have more than one nomination". It isn't a matter so much of determining if you're worthy to be at the academy. It's more a matter of approximately 60% of all appointments MUST be given out and accounted, for allocations prescribed by law. If you can't USE the nomination you have because that "Slot" is filled, it's good to have another one to use, PRIOR to having to be considered in the general pool. Best of luck to everyone. Mike....