I think one factor is probably “advances” in food science. Look how many ingredients go into an average fast food bun, for example… we have so many hyper-processed foods made with not just hella preservatives, but instead of wheat flour and butter it’s like wheat and corn starch, gluten, various vegetable proteins and several different oils, etc all recombined in a rather industrial way. It’s cheaper, and it’s sometimes specifically engineered to appeal to our palates, but it’s been taken too far imo. This is not just an issue in fast food by any means.