I don't know how many arguments I've had with how many partners I've had about this.
It's a dishwasher, not a dish re-washer.
My wife and her family are all freakin' religious wash first, then put it in the dishwasher. My father in law snapped at me about this once. I'm going to send this to him.
If it's not full enough to run, but you also don't want wet food residue to dry on and stick, most dishwashers have a "Quick Rinse" setting that's designed for exactly this purpose.
Scrape, load, and then run Quick Rinse. Much more efficient than rinsing by hand!