What is the use of a restore purchase option for a subscription based app?

If I’m not mistaken, the Apple store requires an app to have a ‘restore purchase’ option. Also for subscription based apps. However, I don’t understand what a restore purchase button does in case of a subscription based app.

If someone tries to re-install the app or installs the app on a different device and tries to log in, the app knows based on the email address if this user is in the database and if he has an active subscription or not. So what is the use for a restore purchase button?

Can someone explain this to me?


Same question here…
Anyone can help?