You’re right that spaces aren’t useful if you’re only in one room(!). Just like a mail client doesn’t need to support mail folders if you only ever have one conversation going on. As others have said, we’ll add the option to hide the spacepanel if you want. Also, you may want to just use a much simpler Matrix client (eg https://hydrogen.element.io - the lightest element!) if you’re only in one room.

In general, Spaces reduce bloat though - they speed up the app by reducing the amount of data the app has to juggle as you filter based on a given space, and they stop your UI and brain being clogged up with irrelevant rooms.