Most probably because like most that have a small world it becomes an opportunity to display expression whilst in a perceived position of authority

 

No only is it the best way, but it is the Proper way to do it, Your Wife Must be physically with you at your passport Control point of Entry.
Otherwise there would be many say OH! Look there is my Wife in the Other Queue, You wave and 6/7 wave back. No! do it Right First time, makes No real difference which Line you take, as long as you are Together.

JP