There is functionality to reopen the last closed window, and also a keyboard shortcut for it. IIRC, the shortcut is Ctrl+Shift+N (on Windows and Linux).
Yes, it is a saving grace and I do use it in case of accidental closure. However, the workspace feature avoids having to manage multiple windows and generally feels snappier because it doesn't have to load/show all the windows at startup. Coupled with shortcuts to switch workspaces, it just feels more organized.