C.E. Evans wrote:
Katra-storage was not a routine procedure and katra-transference to someone else even less so. Until the 22nd-Century, many Vulcans even believed it was just a myth left over from ancient times..
Hmm ok. Sarek seemed to assume right away that Kirk would be carrying Spock's Katra and taking it to vulcan. Maybe that family are just big fans of old mysticism?
It was an ancient custom that hadn't been openly practiced for millennia until Surak's katra was discovered in the 22nd-Century. By the 23rd-Century, it was more well-known on Vulcan.
Even though every Vulcan has the potential to create a katra, I think only a special few (like Surak's) are actually stored on Vulcan and even far fewer are ever rejoined permanently with a living body like Spock's was (Vulcan priests and scholars--and even some cranky Humans--can apparently hold katras for a time until they're transferred safely into a katric ark).