When I'm on a chair with nobody I know, I sometimes intentionally leave my feet on the rest and stare off in the other direction just to see how long it takes others to get torqued enough to say something.
Otherwise I just go with the flow...
On a ride once with a ski patroller, people wanted to lift the bar a few supports away from discharge.
He politely asked, "Would you want to fall from this height?", to which others replied "No".
He said "Rule of thumb: Don't lift the bar any sooner than you're willing to fall from the chair."
I think people get scared that they're not going to be able to lift the bar in time.
With detachables, you could wait until you're skis touch down and still have enough time to lift the bar.