The Great Question. Letter of Assurance (LOA) are given to applicants that WP wants. Many have extreme academic marks, athletes that a program must have or the combinations of a few factors. Since there are no scholarships given, because you pay back the Army with 5 years active service, (there are scholarships available for graduate schools) the academy needs a method to attract young people to apply or finish their application who other wise would never consider WP. Thus a LOA is given to communicate a "seat with your name on it" is there. However, an LOA is conditional, you must finish your application, receive a NOM and stay out of trouble before R-Day.
Continue with your goals and work on your Plan B.
Push Hard, Press Forward