The main reason for using JSP is that it allows web developers to quickly build web pages that interface to enterprise systems. The JSP tags let HTML designers tie web information into corporate business logic contained in Java objects without having to learn all about Java object-oriented programming.

A separate, smaller programming team can create libraries of software components. Then web designers can use those libraries by writing markup tags that they are familiar with. Use of tag libraries is one of the cornerstones of JSP. JSP thus provides a rapid prototyping framework for building two tiers (the client and the front-end server) of an N-tier distributed system.

Servlets can act as a middleware gateway to existing legacy systems, providing an easy way to web-enable your current systems. Furthermore, since all the code is on the server (not the client), when you want to update your application you just roll the code out to a few servers and your entire user base gets the newest code at once.