Much misinformation and misunderstanding on the LOA.
Of course a LOA does not guarantee success as a cadet. Cadets from all States, nomination sources, different SAT scores, grades, races, sizes, gender, etc. either quit or get seperated from West Point. The LOA, however, is a significant and important part of the admissions process.
It seems that some people on the board almost dismiss the LOA as being unimportant. Granted, most new Cadets do not ever get an LOA-it is not a necessary step in being admitted. However getting an LOA is significant because it is West Point's way of telling you that they want you if you can successfully complete your requirements (physical, nomination, PT test etc).
In many ways an LOA means that West Point is now recruiting you. The fact is that that most people with LOAs get into West Point. If you have an LOA and do not get a nomination form your MOC, West Point will make every effort to get you a nomination form another source. They will also initiate and push for a medical waiver if needed.
My advice is to seek an LOA but not be too hurt if you do not get one. However, not getting an LOA is a clear signal that you do not have the strongest file (Whole Person Score). Check with your MALO to see how you can make your file stronger and then aggressively follow-up.
As mentioned on this board several times - one key to getting into West Point is to complete your file NOW. Get all those icons on your portal Green immediately.