But I recognize that's more of a personal style than general usage.
I've been a Mac user since before the system even had proper multitasking, and the general answer to your question is that we would keep open the applications and windows that were useful to us, sometimes hiding an application that we're not actively using and don't need to have cluttering up the screen. Once Mac OS X came along, we would also minimize individual windows we weren't using—and if you minimize a window, then hide the application that it belongs to, that also hides its minimized windows in the Dock.
Also note that for every application up until a few years ago, and for some applications even now (and dependent on a System Preference setting), you can keep an application open on the Mac without any windows open.