I put a RoadID on my wrist years ago, when my wife gave it to me, and have not removed it since. So that's always there.
A couple years ago I ended a ride and wanted a pint from a nearby pub, and they refused to serve me since I had no proof of being over 21. I'm 62. I now carry my driver's license for purposes of post-ride beer. Thinking about it, this may be the only time in 50+ years of cycling that I've actually needed ID while on a ride. Oh, wait, no that's not true. I was stopped by a cop in Florida once and he wanted ID. By law I don't think it was necessary to have, but my day may have gone south if I'd not been carrying it.
Passport when outside the US, but that's primarily for safe storage of the passport rather than for identification.
This topic falls into the category of What might happen and how prepared are you? which is a can of worms of course.