I always see signs such as
Men at work
Children at play
I was wondering why we use "at" in this way. Is it just a formal way of saying Men Working / Children Playing?
Saying "At Lunch" seems sensible, yet even so I would only use this if I were out of the office etc, I wouldnt say "I'm at lunch" if I weren't changing location. If I were to say "I'm At Work" I would use this to inform someone I am at my workplace, not that I am actually working, and no one I know would say their children are "At Play" rather than "Playing".
At to me has always seemed more a word used with a location rather than an action.