There are two reasons we don't like plain username/passwords:
- They are notoriously insecure. If you're running a server with passwords you usually want dedicated staff to deal with account hijackings, which self-hosted servers obviously won't have.
- They are not global identities, i.e. someone else's Sandstorm server cannot authenticate the same identity. So if you transfer an app to a different Sandstorm server (something we aim to make easy), all the identities would have to be replaced with new ones local to the new server, which will probably confuse the app.
With that said, we have been thinking about other ways to solve these problems and we might introduce a plain old username/password option in the future.