1. An individual may not want to share their chats with anyone. They may assume the chats to be privileged, just like attorney client privilege.
2. An individual may still want a legacy contact to get their past chats -- but only some chats, not others. Like you have attorney client privilege, but you can rope in your spouse. But what about inheritors, more so, named inheritors in a will or trust?
3. Law may require some chats to be shared with law enforcement
4. An aggrieved party may want to subpoena the chats
5. Laws may vary from country to country, or even county to county
6. Contracts, such as non-compete or otherwise, require some money to be paid for the agreement. A standard $20 per month may not be enough for that.
And on top of all of that,
7. LLM vendor may have something to hide :) and may not want to share the chats