McDonald's made a name for itself by making fast food really fast, as in, come in, get your 15 cent hamburgers, and walk out. Since all they sold was hamburgers and cheeseburgers (and drinks and fries), they always had them hot and ready to go. Even after they expanded their menu, it was all about hamburgers. But then the Chicken McNugget was introduced in 1981, and they sold like hotcakes, until entire generations of children were raised on them. Not only that, preparing and serving McNuggets at the point of sale was faster and easier than hamburgers, considering all the "manufaturing" was done elsewhere ahead of time.
McDonald's has experimented with chicken for more than 50 years now, because chicken is much more profitable than beef. Other fast food outlets found out how good chicken was for sales, too, sparking an actual trade war. Weird History Food takes us through the history of McDonald's and chicken.
Same is true for gas station hot dogs... That's not really a big selling-point. Other fast food chains made their name on "made fresh when you order it" food that is not precooked and not setting under heat lamps for hours before you get it.