Apple and other Companies Can Deanonymise your 'Anonymous' Data that you share...

TASK: Be aware that when companies say they collect anonymous information on you or your device or habits this may only be partially true. If a company say collects your mobile device ID, or Apple ID or Google ID they can use this to de-anonymise your data. This can be done directly or perhaps in combination with other data like location, sales slips from purchasing the device, personal details already given during registration etc.

Have a look at this about Apple article that explains more....

WHY: Don't blindly assume that you are anonymous, anytime you setup an account you probably let that person or company know who you are. If they then collect 'anonymous' usage data on you then this can be used to find out who you are once their database is hacked or they are forced to handover data.