>>13543081
Oil is liquid at room temp so it keeps the cake soft and more importantly, moist at room temp even when the eggs are fully cooked. Butter in a cake would result in something that is harder and more importantly, drier at room temp.
As far as creaming together the butter, sugar, and egg again it'll result in something that isn't as tender at room temp. Cakes are designed to be eaten at room temp.
And for the cake mix, its just a pre-measured mix of cheap flour, sugar, flavorants, and leaveners. Worse than making your own mix, but for a gimmick cake like this its not really a great sin.
What I couldn't tell you is why this lady left out all the yolks. Thats a huge source of flavor.