I maximize even on large screens because I like to remove the clutter for focus more than because I need the space. I don't want to have a chat window or terminal or anything else distracting me when I read or write something, for example.
So if you used workspaces, you could have an active workspace, and just move the application that you want to focus on into that workspace. Then it wouldn't matter if it was full screen or not. It could be your distraction free workspace.
I do use workspaces. And I maximize the applications because when they're the only one on the workspace I rarely have a reason not to have them fill the screen.
I guess that's down to personal preference. I feel that some applications just don't suit full screen.
Sure, my assumption is that usually people want to multitask during most activities. Reasonable I think, most of the time.