Domestic versus Insitutional Dishwashing
For the latter dishes are normally scraped well, rinsed and or even soaked before going into the DW. The final often quick trip through the machine serves more to remove any residue that wasn't removed by the previous pretreatment and sanitising.
OTHO domestic dishwashers handle things that may or may not be well rid of foods and shouldn't normally be pre-washed/rinsed. Multiple cycles sometimes long do all the work.
Before the advent of enzymes all dishwashing detergents contained chlorine bleach (sanitises and breaks down protein), and caustic chemicals. However the latter often didn't remove heavy soils and or break down protein (eggs, milk, etc..) very well, especially with shorter cycles and less changes of water. Enzyme detergents however give excellent results even at lower wash temperatures so dishes can be done at 120F instead of 140F or above. Drawbacks include having to have slightly longer cycle times that allow time for the stuff to do it's work. Again for domestic dishwashers this rarely is a problem, but you aren't going to find commercial users putting up with that sort of thing.
Never liked chlorine based DW detergents. Always made one's kitchen smell like the cafeteria at school where LCB was for all sorts of cleaning and germ killing purposes. However since most housewives ran their dishwashers overnight after the dinner dishes were loaded and the family vacated the kitchen, the wafting scent of bleach may not have bothered some households.
IIRC the other thing about enzyme dishwasher detergents is they allow machines no longer having to resort to "blasting" dirt off dishes with powerful (and often water hungry) sprays. Enzymes mixed with water are capable of breaking down soils with less force so even a reduced spray can carry the muck away.