Per the Apple article Require a password for App Store and iTunes purchases - Apple Support and the details of the device and Apple ID purchase settings…
You can't completely turn off password protection for paid items on your iPhone, iPad, iPod touch, or computer. On Apple TV, you can turn off password protection for both free and paid items.
If you enabled Touch ID or Face ID for App Store and iTunes Store purchases, you'll be asked to use Touch ID or Face ID for every download, even if the item is free.