The most effective way to understand how much of your activity is recorded is not to read about it. It is to request a copy of your own data from a company you already use. Apple and Google both let any user do this, on demand, for free. What comes back is not a summary. It is a ledger.
What the export actually contains
Open it and the abstraction disappears. Every app you have ever installed, and the date you deleted it. Location history, often stretching back years. Message metadata, and in some cases message content. Every time and place you used Apple Pay. Search history, browsing history, device identifiers, the times your devices connected and where. Things you assumed were transient turn out to be permanent, and things you deleted in the interface turn out to still be there in the record.
This is the opposite of a conspiracy
Many people file this under conspiracy, which gets the situation exactly backwards. There is nothing hidden about it. It is a routine, documented, self-service export that the company builds specifically so you can request it. The lesson is simpler and more useful than any theory: whatever you do inside the software is recorded, and it stays recorded. Deletion in the interface is not deletion in the record. You do not have to believe anything. You can just look.
Awareness, not alarm
This is not an argument to abandon these services. Most people reasonably will not, and this publication is not in the business of manufacturing fear. It is an argument for awareness, because awareness quietly changes behaviour. Once you have seen your own export, you make different decisions by default: what you are willing to put in writing, which account you use for what, when a separate device or a different channel is actually worth the friction. The point of the exercise is not paranoia. It is calibration.
How to pull yours
Apple provides it through its Data and Privacy portal, where you can request a copy of your data. Google provides it through Takeout. Both take some time to compile and arrive as a download you can open and read. Do it once. It is the cheapest and most honest map of your own exposure you will ever get, and it changes how you read everything else here.
The fundamentals layer, in one action
Before deciding what to protect, it helps to see what is actually being kept. Most of this publication is about building structure deliberately. This is the step that motivates all of it: not a claim about what companies do with your data, but a direct look at how much of it exists in the first place. Once you have seen it, the rest of the reasoning follows on its own.