Logs are stored on local devices and many people back them up in whatever cloud (majority not encrypted).

You or the other person could lose the device and someone could use your PIN/password (something as simple as shoulder surfing while you use it). There could also be a leak in whatever cloud service you're using, or the data could get subpoenaed because of some dumb law that gets passed, some rogue employee, etc. It's a huge liability no matter how you look at it.