Why can’t I download freely without asking for billing information??

See -> If you can't make purchases or update apps, including free apps, you need to update your payment method or add a new one. 

See ⤵️

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

What you can buy with your Apple Gift Card or Apple ID balance

https://support.apple.com/en-gb/HT211187

How to redeem your Apple Gift Card or App Store & iTunes gift card

How to redeem your Apple Gift Card or App Store & iTunes gift card – Apple Support (UK)