Everyone else just hasnt come up with a good enough story.
Secondly what is stored in the head of a priest is usually forgotten cuz human memory is flaky and no one is writing anything down in a central db. So every now and then a state attack on the seal work but the everything then reliea on how reliable the memory of a single priest is. Its like a terrible distributed atorage system that is constantly forgetting things. Notice this is literally what large platforms have now built to defend privacy. Its called data minimization and costs a huge amount that they constantly cry about.
So its really funny how the church just stumbled into a solution that is cheap and hard to attack.