hatchback mustang

I have owned cars with trunks and I have owned cars with hatchbacks. Hatchbacks are easily more practical than trunks, and since the rear of a mustang is already styled with nearly horizontal rear glass, I don't understand why there is no liftback. When I first saw a picture of the current mustang style with that little scrap of metal behind the rear glass lifted up revealing a somewhat spacious trunk with no way to get anything larger than a shoebox into it, I though "wow, that's useless".