Yeah, think about it, how do you expect to get real surround-sound through a pair of headphones? - - - it just ain't gonna happen.
Clever wording & marketing by the headphone manufacturers - - and users expecting the real thing without having to place speakers around the room. All headphones should be regarded as stereo, even the simulated surround-sound ones.
If you want to hear sound in front and behind you, put speakers there - - lol