Apple Wallet cards previously had a Share card button on the back. Tapping it let a user share the card with a friend. The feature did not prove useful and was disabled.
On some Apple Wallet cards the feature may still appear, because older iOS versions and Android devices have technical limitations that prevent fully turning it off.
Google Wallet cards do not have a share-card feature.
To distribute loyalty cards and grow your customer base, use the referral promo codes module in the Passquare marketplace.