Why set <@page session = "false">? 
One reason would be performance and memory. 
If you have a page that doesn't need to be involved in a session 
(like say, an about.jsp or faq.jsp) 
then the default behaviour of involving every JSP in a session will
impose the overhead of creating a new session object 
(if one doesn't already exist) and increased memory usage as more
objects reside on the heap.