BBC - Selling Cake Mix: Psychology And Marketing

Cake mixes were introduced in the 1920s and boomed in the 1950s, but sales soon leveled off. BBC reports, "The sales numbers gradually plateaued. Most home cooks were still making their cakes from scratch, and the product had reached everyone it was going to reach.

Even if some people had decided any cake was better than no cake, the persistent sense that something soulless about cake from a box kept many others from embracing it. As they tried to work through this, a man named Ernest Dichter came into the picture.

He was a psychologist and marketing consultant, now known as one of the founders of modern consumer behaviour studies and a pioneer of focus groups."
BBC continues, "Dichter told the cake companies the answer was to take the eggs out of the mix and put them back into the hands of the baker. The problem was that the women who were making the cakes didn't feel emotionally invested enough just adding water, he said. Eggs would make it feel more like baking." 

http://www.bbc.com/future/story/20171027-the-magic-cakes-that-come-from-a-packet