An excellent post... and really good questions.
Let's turn the whole thing upside down, for a moment: Why is it considered almost taboo or "bad form" to be happy and content? How did we get to a place where we are almost shamed for NOT wanting to be part of the "misery loves company" crowd?
I realize the societal cues are strong... as humans we seem drawn to bad news; even the newsmedia knows this and runs on the basic publishing premise "If it BLEEDS it LEADS."
I'd much rather be happy and be around positive people... yet that often exposes me ("us") to being labeled a "Polyanna" or even "irritating." It's almost like "doing well" and "being happy" leads us to feeling a sort of survivor's guilt... instead of feeling happy and celebrating the promotion we get, we feel subtle pressure to downplay it and find ways to feel sorry for those who did NOT get a promotion.
I don't point to these as a lament/complaint... simply as an observation; as well as for further discussion of how to best "derail" this core tendency within to many people's beings. How do we build a better world, in the face of these patterns?