Depends...

On a commuter flight with a 10-20 minute turn around time, deplaning speed is definitely relevant. Not many bags are being checked anyways, and the next set of passengers is already in line waiting to board.

On any flight > 1.5 hours or on a plane bigger than a 737, your point holds. On a 11 hour international flight via a 777, deplane speed is really unimportant at all.

Some of the deplaners hold up the next flight they need to board. Airlines could optimize that.

Not really. Airlines can’t make the layovers tighter because the issue is variance in delays, not problems deplaning.

Also, the US airlines will not hold a flight due to a delayed inbound unless it’s got a shitload of the passengers. I’ve seen Delta depart on time and cause 10 passengers on a delayed flight to miss by only 15 minutes.

Thanks - you made my point more effectively - one slow deplaning flight could hold up flights for those passengers connecting and the results cascade. Most of those connecting flights are probably with the same airline.

Wont help who much? Maybe as you say throughput wouldn't increase because other things need to happen anyway. But passenger latency would improve and that's valuable.

Why is that valuable ? Would you pay double to deplane 5 minutes sooner ?