for me it’s primarily 90’s bikes
the thin walls on the lightweight bars (145 g EA70 Answer Hyperlite etc for example) don’t take kindly to misuse … and same with many of the carbon bars from that era
Oh yes indeed, they scare me too. Used carbon bars scare me even at 5 years old if the bike looks like it's been ridden much.
Aluminum I don't worry too much 'til they're at least 10 years old, but still look for abuse or trainer time.
Luckily the shape of the bars on my 2001 Lemond Buenos Aires was so godawful I had to swap those bars ASAP, and didn't have to fret over the olde bars failing.