Some dishwashers have a built-in grinder (similar to garbage disposal units). Yours might be one of those.

At 15 years old it probably does have the grinder. They starting going away about then though, so hard to say without doing more digging than I care to.

Conversely, my wife insists on not pre-rinsing the dishes and that filter gets real gross, real quick. Unless you mean the spinny arms, never cleaned those before.

Next you’ll be telling me she doesn’t pre-rinse the laundry before putting it in the washer!

I guess the best comparison would be, if you have stuff all over your clothes, you'd probably shake the clothes off before putting them in the washer.

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.

That'd be the equivalent of scraping your dishes, not rinsing them

Well, sorta. I find it easier to rince small stuff off, and that doesn't work with fabric really, but your point is fair.

I don't generally have food waste on my clothes though.

you must not have young kids. Food gets everywhere for a while when they are learning to eat.

Giving the filter a quick wash once a week is way less work than pre-rinsing all your dishes.

Presumably plates had the leftovers scraped off into the compost bin before putting into dishwasher anyways.