The same origin model is about silos of data.

The origin where the data accumulates might (erroneously!) view the data as

"their" data, even when it's their users.

You can see this tension in tech platforms who have signed deals to allow their user's data to be used to train LLMs.

A bargain common in the same origin paradigm: "give me your data in exchange for getting this service for free."

What if it were possible for us as users to maintain ownership over our data?