Commerical dishwashers are better called dish sterilizers. Unlike home dishwashers they are not built to get dishes clean (other than what a minimal rinse does). You have to pre-wash everything if you want it to come clean.
The key is a commercial dishwasher almost never sees "dry food" - the plates either go past a sprayer to get most everything off, or they went into a soaker.
Whereas home dishwashers are designed to run all night slowly recirculating water and removing caked-on grime (with more or less success).
