I don't know if there is a business reason to use the grease they do besides fear of the food Nazis, but food tastes better fried in animal fat.
Yes, it does. I've tried to get the family to use tallow or lard. Bacon fat is nice, but they're squeamish. Of course, I grew up with a farming family, and they all used canola. Go figure.
Part of it is that it was just a pain. They used to have 2 oils, the one with a bit of beef tallow for the fries and the one with none for everything else (because you really don’t want to fry your chicken and fish in beef tallow, it would be weird). Add minimum wage employees that can’t keep track of blue box in this one red box in that one, and using the up at different rates, and different rates of spoilage, plus of course whiny vegetarians, and 2 greases was too much.