I agree that there are few to no events where a tie should be worn but a suit would be inappropriate. There are, however, events where a suit is not required but a fair number of people will still show up wearing an odd jacket and maybe a tie. Some men will ditch the jacket and tie in almost any circumstance where they do not need a suit, while others will continue to dress with a bit more formality. Once you move outside business formal, things are a lot more discretionary these days (you might see dress shirt and trousers, some with jackets, some with ties, and maybe the odd suit at some events). I agree that the middle level of formality has definitely become less important, but rather than thinking of the old middle level of formality as a requirement or dress code, I think it helps to think of it as an option that one may choose. I think odd jackets fall into this discretionary category and casual suits probably do too.
One example that comes to mind: A few restaurants still require men to wear jackets. A suit would not be inappropriate here, but showing up in an odd jacket and tie or a casual suit and tie would both work very well. Of course one could just default to a dark worsted suit and tie (given that this is SF, perhaps I should have added this as a poll option...).
I wasn't doubting the fact that an odd jacket + tie is an option.
My point is that, for some people, it shouldn't be. The look has become a bit dated now and - for the group I mentioned - you'd often be better off in suit & tie or an open collared suit.