Time, said an unidentified wit, is what keeps everything from happening all at once. History is the temporal landscape of a world, what keeps it from being either an endless dreary plain or a chaotic jumble. Even mainstream fiction can't escape history, and sensibly doesn't try. Romance in the broad sense can escape it even less, because it is about big characters who need a big landscape to play in.
I don't mean just the world-saving stuff: the Lensmen*, Hari Seldon, Frodo, or even the next level down, D'Artagnan saving the honor of the Queen of France. Even chicklit, which of the whole Romance spectrum probably veers closest to mainstream, takes place in the big city. It doesn't need a great deal of history, but other subgenres of Romance do, with fantasy and SF being the heaviest users. Moreover, for all the history they consume, only a small part of it is real; the rest has to be made up.
Making up history is obviously easier in some respects. You won't need to google your fingers raw, then end up going to a university library to find out some obscure but crucial fact; if your hero needs a ferry to cross a particular river, you can make sure the bridge wasn't built till later. Even fake history has to sound convincing, though - more so, in fact, than real history, which can always fall back on being, well, true. The Byzantines got the the secret of Greek Fire in the nick of time to save Constantinople from the great Arab siege of AD 674, but do not try this trick at home. Once upon a time you could get away with it, but these days, if your space empire gets free-electron X-ray lasers just in time for its twenty old system-defense ships to zap 2000 Zorgon battlecruisers to oblivion, you had better be brilliant at tongue in cheek or you are toast.
The art of fake history is, broadly, making it sound like the real thing. This doesn't have to mean the pseudo-realistic style, where the Trojan War was really fought over trade routes and the pretty woman was merely a pretext. The history of the Third Age of Middle-Earth isn't Realistic [TM], but it captures the true flavor of early chronicles, history as it should have been. (In particular, Tolkien, a renowned scholar of Old English, wrote the history of Rohan in the appendix in the style of the Anglo-Saxon Chronicle.)
Tomorrow I'll look at a few popular tropes, and as why Edward Gibbon was the father of future history.
* Confession that I've never read any Doc Smith.