Advertisers concerned iCloud Private Relay could put an end to fingerprinting
https://9to5mac.com/2021/07/08/advertisers-concerned-icloud-private-relay-could-put-an-end-to-fingerprinting/
So....
Some European carriers are already blocking Apple's Private Relay feature on the iPhone
https://9to5mac.com/2022/01/10/european-carriers-seek-to-block-iphone-private-relay-feature/
T-Mobile begins blocking iPhone users from enabling iCloud Private Relay in the US
https://9to5mac.com/2022/01/10/t-mobile-block-icloud-private-relay/