Any practical j2ee application will contain several jsp pages.
Data for each JSP has to processed.(either accept and store or retrieve and display)
In this scenario we can�t put the onus of data retrieval and processing on the servlet, which act primarily as a controller in MVC.
Servlet should be thin and delegate most of the task to helper classes.Which does the processing and populate the Value beans and forward to a JSP.
This is the reason we need to additionally add View helpers and Value beans.
I hope this url will give more details. View Helper