I think it’s just a remnant of old school diner cooking. Before McDonald’s industrialized fast food, local diners that served cheap, and relatively fast, food all over the country. It generally wasn’t the highest quality or the healthiest (though diners usually had at least some healthier options like salads and wraps) but it was better than the slop most fast food places produce now and the people cooking it actually had to have some culinary skill. McDonald’s basically destroyed this by automating the process so that hungover teens could do it and make everything basically pre-made microwaved crap.