Racking the shotgun announces:
1. Exactly where you are.
2. That you either keep your arm unloaded or you just threw away one round.
3. That you weren’t serious and you didn’t feel threatened enough to open fire, an important legal element in many states.
Racking a weapon is an announcement that there’s about to be a gunfight. If the other side doesn’t intend to have one, they may choose to flee. If they were expecting one, it has those downsides and more.