Inspired by this post and thinking back to some games I've played which featured huge churches/cathedrals, I came to think: were there other uses for those massive indoors (naves) that some churches had?

Usually I imagine baptizing, marriage, service and whatnot. Was it empty and unused for the rest of the day/week etc.? It seems like a huge waste of a rather vast area that is under a roof and thus usable all year.

Were they used like throne rooms since some Bishops actually and other high clergymen reigned in a pretty mundane fashion, were there markets or something inside?

I believe that not all churches had pews, so there would have been enough space for a lot of venues outisde of ceremonies.