I get you, but I'll explain....(TV's to washing machines...love it)
The cycle takes about 2-3 hours, and we sleep about 7-8. If you leave damp clothes in the drum for several hours, it'll go musty, so you just set everything to start washing at around 4am so when you're up at 7am, you just empty the machine and put your clothes to dry. Just convenience.
Not just convenience, but also economy. Electricity is often cheaper (and greener) at 4am, so you can save money on your electric bill by scheduling dishwashers, clothes washers, etc on a timer.