Minor Currently on the front-end user session (tables UserSession, SessionData) is created no matter what user does. In particular simple site browsing even without form submission creates new session. When spider is indexing website, then session is also created, but spider isn't using cookies or javascript, that's why session is created for each indexed page. At the end of the day we have additional load on database server and a lot of expired session to clean up.
I propose not to create session in case, when all data, that is stored in session could be easily obtained during page load without consuming additional web server resources. This will help us in cases, when user is not logged in.