The main purpose is to manage the voting power for the tokens that have appeared since the Tribes launched.
I talk about it more in the posts below:
https://steemit.com/steem/@abh12345/managing-the-voting-power-of-multiple-staked-tokens
https://steemit.com/steem/@abh12345/managing-the-voting-power-of-multiple-staked-tokens-2
https://steemit.com/tribe/@abh12345/managing-the-voting-power-of-multiple-staked-tokens-3