Every other source game (Portal, Portal 2, Half-Life 2, etc.) has IL catogories for each chapter, rather than each map. This makes sense, as maps that are not at the start of a chapter can only be accesed by console commands, which is effectively cheating. Also, maps where you start crouched or on a vehicle (such as stormdrain and tunnel4) place the player spawn point at a different spawn point when loading in via console rather than loading in from the previous map, requiring these maps to be played individually or else you start with a possibly minutes-long disadvantage when running them.