It's also boring. The "savage, innumerable foreign horde" trope has been done so many times that it's silly to me that they have to stretch history to make the Cuman force into theme park Mongols as opposed to people who had already been integrated in Hungary and serving as part of the larger army (and not much distinguishable from the average Central European troops of the time). Why don't we get more "historically accurate" games where the main antagonists are well-equipped and trained Teutonic knights you're fighting as Poles/Russians/Baltics? That would actually be interesting for a change.