Yes that is a very valid point and does move into the realms of marketing and psycology. Though there will always be a proportion of customers who that does not work upon, which is why I like ticketing systems, which enables the customer to go do something else and pop back in X minutes, as not all want to spend those ten minutes waiting in a queue when they can pop and do other tasks in that time.

Giving the customer the choice can see a balance of best of both, though smartphones have helped in that respect as they afford the abity to do that whilst being in the queue. But time managagment is an artform unto itself.