The thing is though, we only have 2 ears. We don't have 7.1 ears, or whatever - so in theory it should be possible to create the best possible surround experience with only 2 point sources (one for each of our point sensors). Obviously you need clever sound processing for that, but it should be possible...
I don't know anything about the current tech or trends or whatever, but shouldn't it theoretically be possible? about 10 years ago when I last looked at "true" surround headphones they were all terrible. Have things improved since then?
We do only have two ears, but they are designed so that we can locate where the sound is coming from. A whatever point one speaker system works because the sounds are coming from different locations.
From a purist point of view, surround headphones don't work anywhere near as well because there's just the two points of origin, not multiple ones. You have to rely on trickery to fool the brain into thinking that the sound is coming from different locations, rather than just one that's located one centimeter from each ear. That requires a whole bunch of processing, which they aren't keen on. Some people don't mind that, others see it as soiling the audio, if you like.
As for 'true' 5.1 headphones, they're no different. Still cheap multiple drivers crammed into 2 ear cups. Some people still like them and probably will until there's a simulated surround approach that works for all people; except maybe purists.
Sennheiser's GSX1000 is the best one yet that is affordable, although still quite expensive for what it is.