The reseller that we use (Paddle) has a limitation when it comes to PayPal. 

All subscription purchases (yearly licenses) made via PayPal need to be associated with a credit card, whereas PayPal balances can only be used for one-time purchases (lifetime licenses).

This is a security measure because a card is linked to your bank account, and it can automatically be charged every year for license renewal, whereas the PayPal balance can be depleted and never recharged since it's not linked to the account. That's why a card is mandatory for yearly subscription purchases.

Unfortunately, we have no control over this, since it's a limitation imposed by our reseller.‚Äč