Why is it useful for computers to communicate with each other?

Computers communicating with each other has allowed for many things that we now take for granted. The internet, for instance, relies on many computers communicating with each other to transfer information from one place to another very quickly. Banks rely on computers communicating to run automated teller machines. Stores rely on computers communicating to notify each of inventory and other things. Telephone systems now rely on computers communicating with each other.