This chart reflects what a rebound really is. A defensive rebound means your team is forcing the opposition to take long two pointers (bad shots), which hardly ever result in an offensive rebound, and thus are collected by the defense. The long two really is a poison pill in basketball. Not only does it yield the least amount of net points, but it has a very small chance of becoming an offensive rebound if missed.
To test this theory, I looked at the top 5 teams in terms of defensive rebounding rate. The Timberwolves, Rockets, Warriors, Lakers, and Pacers. The trends were the same. These teams were excellent at forcing a high amount of long two's, and/or the opposition converted them at a low rate. Furthermore, these teams also tended to allow either a low amount of paint shots, and/or a higher amount at a higher shooting percentage. A combination of these factors made for a team that turns a large amount of available rebounds into defensive rebounds.
I did the same for offensive rebounds, looking at the shot locations for the top 5 teams in terms of offensive rebounding rate. The Grizzlies, Jazz, Cavaliers, Timberwolves, and Nuggets. The expected trends were again observed. These teams tended to take a high volume of shots inside the paint, and/or convert at a very low rate, leading to more offensive rebounds. These teams also tended to take a low amount of long two pointers, further inflating their offensive rebounding opportunities.
Though fairly cursory, this study serves to highlight some important points. Rebounding, both at a team and individual level, can be less about skill, and more about the kind of defense/offense you play. The Miami Heat are currently the worst offensive rebounding team in basketball. Is it because they can't get an offensive rebound? Maybe. Or, it could be that they shoot such a high percentage in the paint, that there simply aren't that many good offensive rebounding opportunities, and thus their numbers are deflated. Contrast this with the Timberwolves
(Kevin Love), who can miss 2-3 shots at point blank range, rebound them, and then finally make the easy shot. They are essentially be rewarded for their ineptitude, and have inflated offensive rebounding numbers.
This post was a bit hard to follow, so lets recap. There are certain shots in basketball, such as those in the paint, that yield offensive rebounds at a much higher rate then normal. Teams that have a lot of paint attempts, or shoot badly in the paint, will tend to have inflated offensive rebound numbers. The same is true for defensive rebounds. If your team forces the opposition into a lot of long two point attempts, and cuts down on their touches in the paint, you will likely have higher defensive rebounding numbers.
Rebounding is certainly a skill, and a valuable one at that. However, a significant amount of rebound accumulation is less to due with this skill, and more to do with the shot selections of both teams.