Answer:
Yes, sometimes.
Step-by-step explanation:
If you intend to keep the dishes in the dishwasher for an extended amount of time before running a wash cycle, then yes it may make sense to pre-rinse the dishes. If you are running the dishwasher within a few hours of loading it, rinsing dishes may not be required – unless they are extra dirty. It's always a good idea to remove food from dishes before using the dishwasher.