Use case for passing subscription data into subscribe success page

Hello just upgraded to v1.1.9.4: What the possible usage for this?

You can also pass 'Email' and 'listID' data into the 'Subscribe success page'
Example:
http://domain.com/subscribed.php?email=%e&listid=%l
%e will be converted into the 'email' and %l will be converted into the 'listID' that unsubscribed.

Thanks,
Guille