[dragonwriter]

> Why should banks be able to do this, but not other companies or even private persons?

Other companies besides "banks" (savings and loans, credit unions, etc.) can. Other other companies and private individuals only can't in the sense that there are rules governing this to prevent abuse, and if you jump through all the hoops required to do that, you have become a bank, savings and loan, credit union, or some other entity allowed to do it. Banks, etc., are just the name given to entities that have met the requirements to engage in particular activities.