I typically encountered gamma distributions to model response time after a certain event. As far as my statistics goes, that is its natural place. However, in a recent piece of work of mine, I found gamma distribution perfectly modeling the number of order lines within a store order. Why is that?
Definitions for the general reader: when a customer places an order for multiple items of different sorts - say 2 pairs of socks of the same brand/color and 1 shirt - then you say you have two orderlines, one for 2 socks, and one for 1 shirt. A store typically places an order with tens, hundreds or even thousands or orderlines to replenish its stock.