I think the Pacers are just pursuing a contrarian strategy that works for them. All things being equal, threes are more efficient than midrange shots, which is why teams like Houston almost never take midrange shots. But wide-open midrange shots are more valuable than contested threes, and as more and more NBA defenses give up the open midrange shot in exchange for taking away threes and layups, it makes more and more sense to take those shots, only shooting enough threes to keep the defense honest.