Originally Posted by
Scots_Al
Though, of course, if you had a checked bag in the hold, that would need to be found and offloaded; this has been standard since Lockerbie. More than likely the Captain was doing his best to deter people from stepping off the plane for this reason.
OP was at JFK. If this was a US carrier, that silliness was stopped in 2003 for domestic departures and it would not likely occur in this situation for an international departures. This occurred when the US moved to 100% screening of checked luggage.
While this would have been an issue for BA or on departure from the UK, that is all due to antiquated rules and lack of technology.
It is fairly routine for rolling departure delays to occur. It would be interesting for OP to post the carrier and flight. Most often, the Captain will advise passengers that they may deplane but do so at their own risk. For a smallish aircraft, it may be possible to push in <5 minutes so if the Captain obtains clearance, it is easily possible to depart with passengers standing around. For larger aircraft, it would be normal to advise that passengers should not leave the gate area and that while every effort will be made to make announcements in the gate area, there are no guarantees.