Why am I stuck using my Apple Cash on my Apple One subscription?

As I was reconciling my Apple Card statement, I realized my card was no longer being charged for my Apple One subscription. After some digging, I realized the fee was being deducted from my Apple Cash balance. When I navigated to the Apple One subscription payment settings, Apple Cash is listed first and I was notified that I could not re-order the payment priority. My intent was to save my Apple Cash to put toward a larger purchase, not have it drained by $20 each month against my wishes. This began happening in March with no warning. What gives?