That depends on how broad you want your scope to be.

Imagine Air Canada with Gate D76 on a B777-200LR to FRA and then on Gate D78 a B777-300ER to London-Heathrow boarding around the same time. There is nowhere near 600 seats in that area. Why not? Because the 600 people were supposed to wait in the Central Waiting Area.

The congestion in the gate area is still a problem and a direct result of the initial plan of Call-to-Gate. There is simply not enough room at many of the gates to just add more seats to solve that problem; it was a design problem from many years ago in the planning stages.

How much money do you now have to spend to change it? Umm, not enough because the whole design/concept would need to change and it is too expensive to start over.