Environment Affects Learned Behaviors
Just because a bird does the behavior in one environment we cannot be assured they will do it in all without training them. You will not likely have to teach the entire behavior from square one, but breaking it down for a few reps to ensure success will likely need to happen. Even with an influx of bystanders and other environmental factors can cause birds to not put two and two together.
But once the behavior is learned in a few different environments, and even by a few different people, the bird will learn to preform the behavior when asked no matter where they are or by who. It helps for a more reliable and deeper understanding of the behaviors you’re asking.
But sometimes, we don’t want to teach behaviors in different environments or only have our birds respond to us. There are a verity of factors to why we would want to do this.