Advantages and Disadvantages of Structured Analysis
With time, you will find out that most customers understand structured methods better than object oriented (OO) methods. As one of main reasons of modelling a system is for communication with users and customers, there is a benefit in providing structured models for information exchange with customers or user groups.
In fact, specifications are typically in form of a simple English language statement of Work. Thus, the system to be built, understood in terms of requirements (functions the system has to perform), which is why this naturally leads to a structured analysis, at least at the upper most level. Specially structured methods (functional decomposition) provide a natural vehicle for modelling, discussing and deriving the requirements of the system.
The difficulty with structured methods is that they do not readily support use of reusable modules. The top down procedure works well for new development, but does not provide mechanisms for "designing in" use of existing components. The top down procedure of functional decomposition does not lead to a set of requirements which map well to existing components.
When requirements do not map cleanly, you have two options: either you do not use existing components, or force fit requirements to the existing components and "somehow" deal with requirements which are only partly covered by existing components, which does not lead to a good successful system.