I have no idea what that is, but I speculated a bit just for fun:
My first guess as to why would be that offense is more volatile than defense, because it's based on shooting, which is an iffy proposition for even the best shooters in the world. What that means to me is that if your team's main thing is being able to score like crazy, and that's how you intend to win, you will still have games -- every team does -- where the ball does not go in the hoop as much as normal. Those games will be losses for you against good opponents.
That prompted several comments and e-mails, including one from TrueHoop reader David, who sent a fascinating e-mail, including this point:
Defense is dispersed, while scoring necessarily depends on individual success.
Sure, Pick and roll, read-react, triangle, and flex continuity all depend on multiple people fulfilling their roles. The ones who do it best (Re: Phx, Dal, Utah) certainly have lots of guys helping and scoring.
But all offense leads to one moment, securing a single shot for a single player in a desired manner. This makes the impact of offense localized to the individual at any one time. Everyone in the NBA can and does get a chance to shoot (okay, maybe not Ben Wallace), they can at least get the ball in the hoop with some frequency. But the shot still remains, at its heart, and individual act.
In contrast, by simply bumping someone off a screen, Rondo can dramatically decrease the likelihood of the opponent aligning for its highest percentage play. He can do this as his four teammates simultaneously occupy similar, productive roles.
Jason Richardson cannot help “guide” Amare’s post-up if he is on the opposite side of the floor. He cannot increase the likelihood of the Suns scoring on that particular play to the same degree his opponent can decrease the likelihood of the Suns scoring. And for the defense, this happens on every, single, play.
David was making a subtle series of points, from which I extracted this one little aspect.
However, think about this aspect. Good defense is just about always about every player on your team doing things well. Good offense, on the other hand, can be about a few players on your team doing things well.
Forgive me this analogy: Offense is like breaking out of prison. To do that, you just need one person to figure out the weak part in the security system. Defense, on the other hand, is like keeping people in prison, which means knowing that every single wall, fence, floor, ceiling, security guard, door, window and everything else has to work perfectly to keep people in.
Another analogy, this one likely less offensive to the NBA: Hold some water in your hands. If all of your fingers are in on the project, it's doable. But if, say, you need your index fingers to type a 700-page book (Bill Simmons has actually done this, with two fingers) then you can't hold any water at all.
It's not hard to see that keeping people contained is something that will always require a lot of cooperation. While busting loose is something an intrepid prisoner, drop of water, or NBA scorer can do alone or with just a buddy or two.
And while I still can't pretend to know why defense seems to matter a bit more than offense, to my guess of offensive volatility I'll add a new second guess to the brainstrom session: Maybe good defense is a marker for good teamwork.
In other words, maybe you win titles with good team cohesion on the court and good coaching. Maybe those are the teams that hold up the best in the stress of the playoffs, with its Game 7s, finely prepared opponents, fired up crowds, physical play and endless adjustments.
And maybe defensive efficiency is a marker for which teams have good coaching and team cohesion. In other words, of course the defense itself helps, but maybe showing you can play good team defense is also a way of showing that you're a good team, a team that's prepared to hang together when the going gets tough, and maybe that's really what's winning those titles.