From what I have gathered, reason vests are popular in SF is due to daily weather fluctuations since they are light weight. I did not know they were popular in other cities/metros too. Especially in finance sector.
One of the only interesting observations in the (awful, just awful, I cannot emphasize enough how bad it is) sequel to The Prep Handbook is that synthetic fleece had, since the first book, became a hugely popular exception to the usual prep-set rule of "no synthetics", largely for practical reasons (at least at first). I wouldn't be surprised if it's a bit of dressed-down prep fashion being expressed or imitated, at least by a certain set of the folks wearing it. Finance'd be the right crowd for that.
[EDIT] that is, The Official Preppy Handbook. The sequel's called True Prep and is, again, awful, do not read it, it has none of the fun, well-voiced humor of the first, it's bad, bad, bad.
I work in finance (in the midwest), and for some reason, all of the offices I've worked in seem to be kept at an unreasonably low temp, like 68F or lower year-round. That would be fine if I was active, but I'm sitting at a computer from 830a-500p. I've routinely been cold enough to start shivering or to lose dexterity in my hands as they stiffen from the cold.
I can't wear sweatshirts at my current job, but used to at my 3 previous jobs. Now, it's a button down shirt and either a sweater or vest. Ive plenty of both, but none corporate branded.
Vests are nice in that they can easily be removed and put back on.
Most of my sweaters are partial zip. I can't easily remove one without my shirt and undershirt coming with it (I'm a guy, but I still think its rude to go flashing my bare chest & back in an office).
[EDIT] that is, The Official Preppy Handbook. The sequel's called True Prep and is, again, awful, do not read it, it has none of the fun, well-voiced humor of the first, it's bad, bad, bad.