why can’t i download apps without billing information

There are normally some hoops you can jump through as you create your iTunes account that workaround the need for a payment card or bank account, otherwise once the account is set up the iTunes or App Store may still expect you to provide one, even if you are obtaining free content, which you can later remove. If you don't have or want to use a credit/debit card at this time you can try this method using iTunes on a computer...

1. Enable the menu bar if needed with Ctrl+B (only applies to some builds of iTunes 12 for Windows)
2. Sign out of the iTunes Store from the Store/Account item on the menu bar
3. Go to Music > iTunes Store home page
4. Go to Quick Links > Redeem
5. Sign in with your Apple ID
6. Go through the screens, accepting the EULA, etc. You should arrive at a Review Payment screen where one of the options is None - select this and continue. You shouldn't actually need to redeem a new voucher/card.

It is worth noting that one of the functions of the registration is to prove you have a valid billing address in the region whose store you are trying to use. You might also have difficulty selecting None as an option if you have any active subscriptions (see If you want to cancel a subscription from Apple - Apple Support), an outstanding debit balance to the iTunes Store, there are unreleased authorization holds on the card (see How apps, content, and subscriptions from Apple are billed - Apple Support) or you are trying to switch to one regional store while being in a different region. See Remove a payment method from your Apple ID - Apple Support for more.

You would also need to add a payment method to commence a free trial such as Apple Arcade. There will be an availability check for the value of the subscription to ensure that you have an active payment method when the subscription comes up for renewal. Some financial institutions will incorrectly treat these as actual payments which they later remove from the account.

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