You are correct, shouldn’t need to, but in reality it is sometimes to often necessary.
One thing i have noticed is that the first time just about everything comes out clean, but on subsequent washings not so much, its almost as if you need to wash by hand after so many loads to ‘refresh’ the cleaning power of the dishwasher…
Well, peanut butter when it’s on a spoon in the concave area :). Then what is the problem food?
oatmeal, dried sauces, cheese, cookie sheets with baked on black stuff, thats just off the top of my head.
I don’t get what so gross about washing dishes? Ten minutes earlier you can’t get enough of what you’re eating and now the leftovers on the plate are disgusting?
I clean what’s needed as soon as I finish my meal, wifey doesn’t need too clean my shit and dishwasher is just sitting there thinking it’s useless. Literally five minutes.
Buy yourself some nice dishwashing gloves. They make it much easier on you. We do +- 80% in the diswasher, and the rest by hand, becaus they either don't fit in the dishwasher or they aren't meant to be put into the dishwasher.
And don’t believe the manufacturers of dishwasher “soaps” that you can put them in the machine just as they are. And wait for using the machine till it’s filled up properly. It’s better to overcome your “fondness for the mushy goo” and wash that down the moment you bring the dishes into the kitchen, because if you don’t do that at once you might have to use a chisel 
Besides, I like to keep “my” kitchen clean. You might have heard of the expression:“don’t do this (while the missus is) at home”. Things that happen in the kitchen, stay in the kitchen. Besides, I like a clean work environment when I’m baking my ano.