Why is rinsing coffee cups before use important?

Rinsing coffee cups before use is important to remove residual flavors. When cups are not rinsed, any leftover substances from previous uses or from the washing process can influence the taste of the coffee. This means that even if the cup looks clean, it may still have lingering flavors that can alter the overall experience of the beverage being served. A clean slate in a cup ensures that the true flavors of the coffee will be appreciated without interference from any unpleasant or unwanted flavors.

The context of other answer choices helps clarify this importance. Preparing them for serving might imply a general cleanliness, but it doesn't specifically address the flavor aspect. Ensuring they are sterile speaks to health considerations, which, while important, is not the primary reason for rinsing in a coffee-focused scenario. Finally, making them appear clean is more about aesthetics than functional flavor integrity, which is ultimately why consumers drink coffee in the first place.