I remember Spam fried in butter every now and then, circa 1956 - 1961 or so. Don't think it was purely economics. Our refrigerator had only a small compartment as a freezer. Just about big enough for an ice cube tray and a pound or two of meat. Because of that, there was a lot of canned meat going on, Spam, canned ham and corned beef and even canned whole chickens Mom would make use for chicken and gravy. Also canned salmon (double yuk).