why can't I use my apple account balance before my credit card?

See this article:

How App Store and iTunes Store purchases are billed. Click here --> https://support.apple.com/HT201359

Some purchases aren’t charged to your Apple ID balance

- If you're in a Family Sharing group, purchases are charged to your personal Apple ID balance. If you don't have enough Apple ID balance to pay for the purchase, the remainder is charged to the family organizer's primary payment method.

- You can’t charge gifts to your Apple ID balance. If you send a gift or gift card, your primary payment method is charged.

- Some subscriptions might not be charged to your Apple ID balance.

I am having a similar problem. My account has a credit over $45 but my previous purchase of just over $25 went to credit card not credit. How can this be fixed or reversed so it does not charge the credit card?

This is not the first time this has happened, how can this be prevented?