All moments need a start and end event in order to be completed.  Sometimes users can navigate multiple ways through a moment and end up in different places within the app.  In those cases, you need to have multiple ends in order to account for all possible user paths.  For example, if the startup can end on a login screen (if the user is signed out or doesn't have an account) or the home screen (if the user remains logged in), you need to have multiple ends to accommodate both paths.