If the IFF rule is in place to prevent multiple plays on R's... Why is it limited to 1st and 2nd and 1st, 2nd, and 3rd? Why doesn't it include a runner on 1st alone?
TIA

Because if the BR opts not to run, s/he doesn't deserve to be protected. When it is 1st & 2nd, there are two runners other than the BR that can be hung out to dry.

Why doesn't it include a runner on 1st alone?

The purpose of the infield fly rule is to prevent the defense from getting an out they don't deserve. They are entittled only to the out on the fly ball. But if they deliberately let it drop they could get a force out on runners that were trapped close to the base due the fly ball.

However - you are not going to get the out at 1B on the B-R. By time you let the ball drop, throw to one base and relay to 1B, the B-R is long past the base. (Remember that B-R was running all the time the ball was in the air, while the other runners were stationary.) Thus with a single runner on base you cannot drop the ball and get two outs.

But with two or three runners on you can easily let the ball fall and fire to two bases for two outs.

By making the Batter an automatic out, the force has been removed, preventing multiple outs.

WMB

The IFF is to prevent a triple play.

You're one out too many. It's to prevent a cheap double play. If it was to prevent a triple play, the IFF would only be in effect with no outs.

Bob

Re-phrased: The IFF also prevents a triple play. ;-)

To prevent means it could happen..IFF triple-play cannot happen...re-phrase again.

HUnnh? If there was no IFF rule, with no outs and 3 runners on, an infield fly not caught could easily become a triple play, since all base runners would stay at the previous base. Throw home, then third, then second; three force outs on runners who wouldn't run. The IFF also prevents that triple play, thus Tony's statement requires no rephrasing.

First, a triple play CAN happen on an IFF...

Second - his point was that the existence of the IFF rule prevents the defense from getting an undeserved triple play (just as it prevents them from getting an undeserved double play!)

"The IFF is to prevent a triple play."

This statement, in itself, means the rule was written to prevent a triple play, ONLY. That is incorrect.

Bob