I have been reading and re-reading the posts on Brophy's Blog about his visit to LaTech in particular the post about stripping down the Air Raid offense available here. One of the major points taken away from this post is how Tony Franklin and other Air Raid coaches are limiting defenses by limiting their offense. The offense doesn't feature 2 back sets, TE's, unbalanced formations, or even a great deal of motion. The primary reason is the more you do offensively the more looks you could end up seeing from defenses. The limits they place on their offense means that you can really simplify the fronts your offensive line has to be prepared to block and what coverages your QB and receivers must prepare against. Another highly successful offensive coach that limits defenses is Paul Johnson at Georgia Tech. Triple option teams thrive on defenses that have responsibility breakdowns and work to create those breakdowns. As a result defenses are forced to limit their game plan to insure that breakdowns from excessive defensive scheme don't occur. Compound that with the fact most defenses that face GT only see the offense once a year and you have a recipe for defensive limitation.
I believe that this same philosophy of limitation can be applied to defensive coaching. If a defense can effectively blitz it limits what an offense can run. Blitzing makes defensive players the initiators and the offensive players are forced to become reactors. This is a major role reversal from the normal situation players find themselves in. Normally a defender is taught when the offensive player does X I do Y (think guard reads). However when a blitz is called the defender knows where he is going before the center snaps the ball. Offensive plays that try to manipulate defensive reactions like draw, misdirection, and play action passes can therefore be severely limited by the blitz.
Against drop back pass, specifically 5 step, the defense can limit the deep throws by pressuring. It is difficult for an offense to get a receiver down the field to run a deep curl/comeback, dig, or other intermediate breaking route against well executed pressure. Often the pressure forces a hot throw. This means that by pressuring or bluffing pressure the defense can dictate where the ball is thrown. If the defense knows that pressure will induce a hot throw it allows pressure coverage periods in practice to be more focused and efficient. It also takes a great deal of practice time for an offense to become efficient at completing hot routes. Every period and rep of practice time that an offense spends on hot routes is time they cannot commit to practicing the rest of their offense. This means the offense can try to call plays they haven't spent much time practicing or mark them off the call sheet. Either way I believe this is a defensive victory in the planning and practice phase. Limiting the 5 step passing game to quick throws makes defending the 3 step game easier as well. Defensive players can anticipate early throws and the practice time for pressure coverage against 5 and 3 step can be streamlined.
By limiting what the offense runs the defense can make better use of practice time and get better at stopping their opponent's base plays. It is difficult to succeed on defense if your opponent has every play in their arsenal available. Blitzing is one way a defense can limit the offense and improve practice efficiency.