Immigration/passport control upon exit of some countries and not others?
I am interested to know why some countries have immigration/passport control upon exit of the country and others do not. The USA and the UK do not have exit immigration/passport control and there may be other countries that do not. All of the European (not intra-Schengen), Middle eastern, and Asian countries I have visited have exit immigration/passport control. I wonder why this is. Any thoughts?