The ITKF is a multi-style organisation, with members from Shotokan, Goju etc...
Now think how difficult it would be to judge Kata from different styles, especially the one's that you do not know, that's why the criteria for judging is on techniques and performance (power, fluidity etc) and not on the Kata its self (like I tried to explain on the way back from Blackpool this year).
So, Kitei was invented so that everyone, no matter which style they belonged to could have the same crack at the whip with the same Kata, sort of make it fair for everyone.
It's changed every three years again for this fairness, so that everyone who performs it has had the same amount of time to practice it.
Makes sense?
If not let me know and I'll try to explain in Azzy.