The UK and some other countries, Australia, Japan, Canada, New Zealand, Monaco, and Taiwan, have a reciprocal agreement with each other to allow students from the given countries to obtain visa's for the other countries for up to two years and work within those countries.
Opening this up to the US would be a great boon to people who may not have enough money to completely sustain themselves through a 6 month or 1 year period without working. This would also be especially useful for students who want to take a year off of school and travel, and could allow them to use their time traveling and working instead of having to choose if they aren't wealthy initially.