When you play back Dolby Atmos material, this feature sort of emulates having a surround sound system. So, even though you only have two earbuds, sounds do seem to be around you (coming from behind etc.) And if you move your head, the sound source stays the same, enhancing the illusion that there are 5 speakers around you and if you move, the sound changes.
The emulation is convincing and well executed, but it is still just a gimmick that only really works when playing back Dolby Atmos movies.
What "the point" of headphones is, is of course subjective. But I'm going to guess that for most people, the point of using headphones is have their audio portable and/or to not disturb other people. I don't think many people use them because they explicitly like the experience of audio playing "between the ears".
As to "why", people might actually prefer the (emulated) experience of a point sound source, as it could closer resemble talking to someone physically present (calls) or listening to a live performance.
The emulation is convincing and well executed, but it is still just a gimmick that only really works when playing back Dolby Atmos movies.