Apple Explains Why ‘Allow Apps to Request to Track’ May Be Grayed Out on iOS 14.5 - MacRumors

On devices with the “Allow Apps to Request to Track” setting grayed out, all apps that request to track are denied permission by default and cannot access the device’s random advertising identifier, known as the IDFA, according to Apple.

This is default for all kids with Apple IDs. Way to go, Apple!