Actually, a lot of merchants need to know the sender's name as well as the control number in order to collect the money.

You are right about the foreign worker thing though -- people send lots of money (called remittances) to countries like Mexico, Central America, and the rest of the world, many of them using Western Union because of convenience and speed of transfer. El Salvador, a tiny country of just over 6 million people, has incoming annual remittances of over 2 billion US dollars!

Also, the regulations against things like drug dealers, money laundering, terrorists etc, are usually for amounts larger than US $10,000. Any cash or cash equivalent (which includes WU) transfer over that amount has to be fully declared.