It is only done when the runner is trying to break up a double play by running into the infielder. It is done to prevent injuries.
I’ve seen it happen even when there’s no one near sliding into second. I also hate the call where the guy making the play at second or third or wherever goes to turn a double play and drops the ball, but because it was “on the transfer” the guys out. I don’t care if you’re transferring the ball, you’re a freaking Pro don’t drop it! I’m a girl and we played fast pitch softball and there is no proximity to the bag rule or transfer rule. And at least a couple times a year you get an ump that refuses to call the proximity rule so either do it or don’t! I went to HS for an entire week with a huge black eye because we turned a double play the right way! If a girl can handle it, an adult male should be able to!