X probably stands for the idea of his “everything app”.

I self-host a Bitwarden instance at home. Passwords are sensitive data, which I do not want to put onto any cloud, where I do not have control over them. I know E2EE is a thing. However, I still have more control with self-hosting. Additionally, E2EE means nothing to me if the client application is proprietary (most password managers are, unfortunately).