Well it is the latest trend, along with AJAX, of course.
Nevertheless there are good reasons for Service Oriented Architecture as this very good article about Service Oriented Architecture by Dr. Hao He makes clear.
As Dr. He points out, our aim in information management is to make systems whose complexity is a close match for the complexity of the information we are managing. Our systems need to be complex enough to deal with the complexities which they are modelling, but should be no more complex than that.
Service Oriented Architecture is a design principle that calls for "Loosely coupled" services.