I don't do any bookmarking or tagging, so either it's an open tab or something I can dig up in the history. So I tend to keep tabs open if I think there's a chance I might need to refer to it soonish. Or I just forget them after my focus moves on to something else.
"Bookmark, tag, and close" loses active state and requires a full page refresh. It also loses the history (where it was opened from). Bookmarks are useful, but they're not the same thing as tabs.
