Why do all the other supermarket checkout queues always move faster than yours?

In a new book «Why Does The Other Line Always Move Faster?» author David Andrews explains:
«Our minds are rigged against us. Regardless of time actually spent, the slowest line will always be the one you are standing in.»

He adds probability is also against us, explaining if there are three queues, there is a two in three chance one of the queues will be faster than yours, while you only have a one in three chance of your line moving quicker.

Source: http://9gag.com/gag/a3LgXee