So applications can stop the connection. Required for https://github.com/andyholmes/gnome-shell-extension-mconnect/issues/32
Why is this needed in the first place? With the current design, devices automatically try to discover and connect to each other. This means that if we added a 'disconnect' button, after a while the devices would connect again.
At least when using the button on Android, it does not happen. And at least the GNOME extension runs the device discovery only for a limited time and only if you click on a button. So when implemented a disconnect would mean "disconnect until I click the button to reconnect again". Reasons for disconnecting a device are diverse, e.g. saving power or so.