Boeing has been toying with a blended wing passenger aircraft for some time. There are some considerations once we want to put people in one of these things that don't come up when they are bombers and freighters.
People like to be able to see out, through real windows. Or at least have one nearby. It's a real psychological hurdle, believe it or not.
People don't like to sit too far out from the aircraft's roll center. They get kinda squeamish when the ship banks very much. So, they have to sit towards the center - no windows. Cargo goes outboard, but doesn't need windows... hmm...
