Look at it like this. If a runner is on third with nobody out, especially the leadoff hitter (who likely would be a speed guy), the odds say that whether the infield is in or out, he will eventually score, irrespective of who your pitcher is. Therefore, I take my chances with the infield in and at least have a CHANCE of cutting him down. And even if the batter gets a hit past the drawn in infield, the odds are that you'll have no worse than a runner on first with a chance for a DP with the next batter.