I'm not being a pain in your b......t but people say things like "When did last see him? It's been, about an hour ago." or "Why are so tired? I've been to an all-night party, yesterday."?
NOT A TEACHER
(1) If this is another topic, I believe that the teachers want learners such as you and I
to start a new thread. But maybe they will not be too cross with me if I answer your
new question in this thread.
(a) I believe that many Americans prefer "a pain in the a _ _." We can say, however,
"a pain in the neck." When we say "neck," we know that it's a nice substitute for
"a _ _."
(b) It is true that native speakers often leave out words in fast conversation, but I
doubt anyone would say "Why are so tired?"
BUT they would look at you and
exclaim: "Why so tired?" (Why (are) (you) so tired?)
(c) I doubt that any native speaker would say "When did last see him?"
Tom: Have you seen Joe recently?
Martha: Not for a long time.
Tom: Really? What's the last time?/ When was the last time? When was it?