Here I am, doing my best impression of a bat.
Why in the world do we do this? Three main reasons:
1. Strengthens the upper body. This includes your back, arms, hands, and upper body in general. The older I get, the more this becomes necessary.
2. Develops grip strength. Think: Carrying suitcases -- or bales of hay. Or opening a jar of pickles.
3. Promotes bigger and stronger forearms. The latter are vital when climbing the Alps.
WARNING: If you are a beginner, DO NOT jump up and grab the bar! Instead, use a platform to reach it.