The rule exists solely to prevent the defense from executing a double play or triple play by deliberately failing to catch a ball that an infielder could catch with ordinary effort.

Why is there no infield fly rule with runner on first?

Why is there no infield fly rule with a runner on first? If there were just a runner on first the only advantage the defensive team would have by letting the ball drop is to get the lead runner out at second.

What if infield fly is not called?

If the conditions for an infield fly are not met, (runners not on 1B and 2B or bases loaded less than two outs) or it is a bunt, then the batter is not out.