Family Sharing - Payment Sharing

How can I use my own payment method to get an app if I am on family sharing/payment sharing? We do family sharing with our Apple devices and also agreed to payment sharing for ease in use and sharing content. Unfortunately, every time my SO wants to get an app that needs payment he needs to get a code from me (the organizer). Is there a way around that?? Why would it force the spouse/another adult to get a verification code every time?? and why can't we use our own/another payment method when purchasing some apps??