Starting with iOS 14.5, Apple required app developers to notify users about broader tracking so that they could opt-in or opt-out. In 2021, Google apps have stopped certain tracking methods (IDFA) to comply and do not have to show this notification. However, YouTube will soon start asking iOS users if they want to enable «more personalized ads» with the App Tracking Transparency (ATT) notice.
In the near future, YouTube for iOS will show a one-time permission request — do you want YouTube to track your activity on other companies’ apps and websites? — with two options:
This request will not appear for YouTube Premium subscribers and users with child accounts on YouTube.
Later, the user can change their permission through the iOS settings section: Settings > Privacy & Security > Tracking.
Source: 9to5google