I have owned my current dishwasher for about 15 years, and I have never once cleaned it. It's working just fine.
EG, I use the 'weed wacker' to cut up stuff, or I am racking leaves, I get pants with plant debris on them. I tend to shake them off first.
Presumably plates had the leftovers scraped off into the compost bin before putting into dishwasher anyways.