Why is a session stateless?

Answer 1

Session is stateless or statefull based on work to be done. This answers "why?".

In case of a web server each each request we make to the web server is stateless mean independent of another request. Therefore we use $_SESSION and $_COOKIES to keep state of a server script variable across requests.

A work can be performed within a single method invocation(request to the web server), or it may span multiple method invocations(example: statefull bean in java)

If you will read this link http://www.java-samples.com/showtutorial.php?tutorialid=841 and will work on java bean, the statefull nature of a bean will be clear. In this user object(a java bean) has to keep it's state across multiple methods invocation by the client.

Nonetheless all causes related to work we do on day to day basis may be difficult to find out and to interpret even if we find out them.

Answer 2

A session is considered stateless because each request from a client is treated as an independent transaction by the server. This means that the server does not retain any information about previous requests from the same client, and each request is handled without any knowledge of past interactions. However, session management techniques can be used to maintain a sense of continuity and statefulness for the user during their session.