I've recently been reading on session cookies and how they can be hijacked via man-in-middle attacks. It seems this is mainly possible on an unencrypted connection between a client and a webserver.
However, I cannot figure out why, if one is already 'in the middle' of an unencrypted connection, would one prefer to capture the cookie instead of the username & password - a more valuable resource - which should also be sent in plaintext?