It's because NIMBY is equivalent to defection in an iterated prisoner's dilemma[1]. By being NIMBY, you'll be a bit better off today, but because someone else is NIMBY, you'll be a lot worse off tomorrow. YIMBY makes everyone better in the long term.

[1]: https://en.wikipedia.org/wiki/Prisoner%27s_dilemma

Agreed. Why should the city and its residents stretch thin... businesses and newcomers will simply wise up and spread out. Living and working here has become like a high on drugs, and people are doing whatever it takes to get their next hit.

I'd love to see what an intelligent generation does to build up neighboring cities rather than complain about one that would do just fine without them.

It's a pejorative because it is a short-hand for a longer statement: "Yes, of course, we need ${X}, but not in my back yard."

the same nimby who voted no Bart in the peninsula in the late 60's because it would: bring "unsavory" ppl from the east bay "to my snowflake walled community"

you can see the result of that now: diesel caltrain unadequate for ppl to commute with, and crowded freeways