In ye olde days, many RPG systems were constructed as the "physics engines" of the worlds of the game. That is to say, they were designed to describe the physical rules that governed the worlds, even if those rules were necessarily fantastic because the worlds they modeled were fantastic. In many cases, these systems became "universal" because, as physics engines, they could model many different worlds in different milieus because squishiness of flesh under duress (for example) was considered to be essentially the same between those worlds.
Those kinds of rules systems are less common now, with other concerns such as modeling genre tropes or story beats etc... have become popular. And those kinds of games are great for their purposes, but they don't quite scratch that "modeled physics" itch some of us have when we are pretending to be an elf.