Most certainly they will leave you if they need to get moving fast and you are not around. Which can mean the difference in getting airborne in 25min vs 3hrs.

Yesterday I had one going to KEWR that had a 2hr EDCT that got shortened to 20min which if missed would turn into a ground stop. They were boarded at the gate and just needed to close up and push back, which took 10min, then a 7min taxi and 2 min for the runway to clear, take off and tag up ment they barely made it.