Now I don't know which immortals do not use their soulnames as their real names.
Anyway I assume that all elves have soulnames. Except the Go-backs maybe -still thinks it is strange that they can deny their souls name :?
However the reason why the wolfriders hide their soulnames is because they have been threatened in some way by enemies ad revealing their soulname to would be very bad (just look at Winnowil and Dewshine).
So maybe the imortals you have heard of had some reason to hide their soulname.
The Sun Villagers have no reason to hide their soulnames so they use them as their real names.
But it is strange then that there is not a closer bond in the village. Because with the wolfriders everyone who has shared soulnames are very close emotionelly. Hmmm....