How do you feel when someone doesn't greet you?

Yes because it's manners to greet other people in certain settings. Equally some people hold themselves in very high estimation/esteem and think everyone else thinks and feels the same. So not greeting them is an insult to their ego.

I used to care but not anymore. To me its rude for a coworker to ask me a bunch of questions without at least greeting me first.

I was raised to say hello.

Depends on who it is and where you are, most of the time I don't care, except the fast food employees standing at the register waiting for You to say something, that really annoys me

Relieved usually

Alleviated... Won't have to exchange meaningless pleasantries with a filthy human 👽

i plan a bloodthirsty revenge in my head..