alt Hacker NewsWhat if you get a large number of people calling at very particular times? E.G. what if you're getting far more calls at 09:00 than at 09:15? You can't hire agents just to handle a 15-minute surge.
Erlang's model assumes that the world is static or at least predictable; it doesn't take into account things like the superBowl, a hurricane cancelling 90+% of flights from a major airport, or a much-larger-than-usual number of customers trying to cancel because of a previously-confidential price increase now being publicly announced.
Baseline demand affects the numbers much more than the unpredictable spikes do. You can come up with edge cases if you like, but the reality is that it all averages out pretty well with large volume.