You can choose which category of users Save for later is active for; Only users who have registered on the site, or for all users.Of course, it is better to have Save for Later active for all users so that users are encouraged to buy.
By enabling this option, you force users to register or login to use Save for later. If this option is disabled, it means that all users can use it.It is better to disable this option because registration requires time, and it may discourage the user from purchasing and continuing the process.