End-to-end encryption is one of the main features of the product. Since the key is user-controlled, there will always be something that the user must keep and never lose. For this first version, we chose to make that thing the user’s own password.
Other end-to-end encrypted apps (such as password managers) have the same requirement. Sometimes the password is resettable, but you have to keep another key. But there’s always something that would lock you out if you lose it.