https://delishably.com/dining-out/five-disturbing-facts-about-the-mcrib
“Most people would be extremely unhappy if they were served heart or tongue on a plate,” he observed. “But flaked into a restructured product it loses its identity. Such products as tripe, heart, and scalded stomachs are high in protein, completely edible, wholesome, and nutritious, and most are already used in sausage without objection.” Pork patties could be shaped into any form and marketed in restaurants or for airlines, solving a secondary problem of irregular portion size of cuts such as pork chops. In 1981 McDonald’s introduced a boneless pork sandwich of chunked and formed meat called the McRib, developed in part through check-off funds [micro-donations from pork producers] from the NPPC [National Pork Producers Council]. It was not as popular as the McNugget, introduced in 1983, would be, even though both products were composed of unmarketable parts of the animal (skin and dark meat in the McNugget). The McNugget, however, benefited from positive consumer associations with chicken, even though it had none of the “healthy” attributes people associated with poultry.
https://www.chicagomag.com/city-life/october-2011/the-invention-of-the-mcrib-and-why-it-disappears-from-mcdonalds/