I have to disagree with the comments about the IBO distances being to short. First the IBO stands for International "BOWHUNTING" organization, its not field archery.
Second, unlike field or other target competitions, the yardages in the IBO are unmarked, requiring not only the ability to shoot but the ability to determine yardage as well. Also, the World courses are no picnic, uphill/downhill, dark/bright targets make even short distances challenging.
Finally, is the biggest reason, only the top shooters avg a per target score of 8 or more(8 being a vital shot). IMO, if you increase the distance to the point where even the top shooters don't avg 8 points per target, that just looks bad . Consider that the compound classes are almost always decided by total X count.