It's simple, physics is lazy, it does the most energy efficient thing possible
Now, I want you to do this quick experiment
Hold your hand in the air for a few seconds, dont support it, just move your forearm up so your hand is in the air
Now, let your hand fall and then rest, which one is easier?
Well, if you found letting it rest easier, then the universe would agree, because spending less energy is the easier option
Like how it's easier to put out a candle than it is to light it
Or how its easier to spill water on a carpet than to clean it up