Why do I have to pay this every month

Why do we need to pay $2.99 every month !

Do you have an iCloud subscription?

Check -> Go to -> Settings -> your name -> iCloud -> if you see 50 GB (or 200 GB or 2 TB) then you have an iCloud subscription.

If you have an iCloud subscription, you will receive a monthly bill from Apple, check your email box.

You pay monthly for iCloud storage.

See this Apple article: iCloud+ plans and pricing -> iCloud+ plans and pricing - Apple Support

All subscriptions, free trial or otherwise, must be cancelled at least 24hrs prior to expiry - as otherwise you will be charged. Subscriptions do not end automatically.

The following links should help you to both identify and manage any recurring Apple service subscriptions associated with your AppleID account:

If you want to cancel a subscription from Apple - Apple Support

Manage App Store purchases, subscriptions, settings, and restrictions on iPad - Apple Support

Subscriptions and Billing - Official Apple Support

View your purchase history for the App Store, iTunes Store, and other Apple media services - Apple Support

Because you are subscribed to something. See if this helps: Subscriptions and Billing - Official Apple Support