Waiting for a train and a guy started chatting to me to pass the time. Told me he had a 51 year old son so he must be in his 70s. When he discovered I work at a university he asked me the question in the subject line.
I asked him what made him say that and he just shrugged. I didn't say so, but I suspect it's because I'm a woman and also his generation.
Unreasonable to be wryly amused/slightly miffed? Not the first time it's happened and always men that say it.
Not that I'm saying there's anything wrong with working in administration either btw.