All it takes is one auto accident in the wrong spot of the road, and you can create a traffic congestion of a few hundred cars.

A 20 minute delay of 1 flight out of is not the same as 1 minute delay for all 20 flights. When a flight is delayed, the gate remains occupied and the ground crew can't move on to the next plane. The passengers on that plane may have connecting flights which then may be delayed. The takeoff order has to be re-ordered. So that single delayed flight can end up scrambling the system for many other flights.

Also, if you treat all non-matched bags as potential bomb threats, you have to call out the police/bomb squad every time you find an unmatched bag.

An if you do find an unmatched bag which is potentially a bomb, don't you have to evacuate the immediate surroundings? How many flights and gates does that affect?

I think it's safe to say that we've all seen how 1-2 cars can stall traffic for miles. Take that practical experience and apply it to airline schedules, and it's obvious why airline hate the idea of positive matching.