MacDonald Douglas/Boeing’s original blended wing body BWB from the late 90’s early 00’s was toyed with but passengers hated it. Most of your passengers wind up in the middle of the plane, far from any windows. You’ve also got issues with trying to get everyone off the plane in an emergency. The FAA has some pretty stringent rules about how long you’ve got to do that. You could, in theory, turn the center of the plane into a giant cryo tank and seat people on the sides near the windows but… well you’re building a huge aircraft and then spending most of the volume on a giant thermos instead of things that make you money.