So a long time ago, when was Army, it was fairly unheard of to make it past E-6 without a college degree. Similarly, it was unheard of to make it past O-3 without a Master's degree. Maybe things are different now, but I'd bet this is a huge reason why you'd get passed over for O-4. It's kinda like pilots. Unless you have some crazy turbine PIC hours with type ratings, usually a college degree is required at some point (to get on with a certain carrier). There are people that make it through without, but they usually aren't the normal over-achievers like you and me, they are a special breed that got extra lucky or were in some specific situation. In the end, not having that can hurt them or limit them...