Navy plays a 3-4 as their primary defense. It doesn't make a whole lot of sense for them to have 4 down linemen when it's almost assured that all the the linemen will be undersized compared to the competition. We'll never have 350 lb linemen so we might as well field 4 quicker linebackers.
Until the Academy figures out how to recruit HS All Americans with the promise of NFL contracts on the horizon instead of manditory naval service, we are probably going to have to count our blessings and stick with the smaller bowl games.