Why is oil added at the end, instead of with wet ingredients?

I am curious about the mixing order, with adding the oil after the flour is incorporated. I did it as instructed, and it actually came out fine. I was worried it would end up tough as the flour ends up getting mixed twice as much as is usual in cake recipes. You did mention that oil in cakes helps lessen gluten development. But still, I am just curious to know why it is done it that order, rather than mixing the oil into the wet ingredients before folding the flour in. :).