As I understand it, Snowdragon is gone for a bit, although I am interested in the details of the milk pouring as well.
I can see a few reasons for wanting apple cores and other fruit debris to go down the disposal instead of in the garbage. We do not currently have a disposal, but I try to recycle and dispose of things with as will waste as possible. Garbage stinks after only a day if you put those kinds of things in and I can see some people wanting them down the disposal instead.
I also HATE dishes in the sink. It is a personal issue for me, but dirty dishes should be in the dishwasher or washed and put away. Clean dishes should be put away not in the sink. Other households do not have to operate this way, but it is an issue for me. My husband knows this and is pretty good about it, but he has several dishes he doesn't like to go in the dishwasher. He will wash them and then leave them in the sink or on the counter. It does annoy me if I am making something and I cannot drain things in the sink or rinse my hands because the sink is full of dishes.
I will admit I have to fight my passive-agressive side to not just drain the pasta or rinse my hands over the clean dishes when I turn around with my hands full and the sink is occupied by last nights dishes. (I haven't done this, but I have to confess it crosses my mind)