It all about casino money for the tribes being split between more people.
If they’re hoping for casino money they should think again. There are about 6000 tribes but only several hundred casinos. And only a handful of the casino tribes disburse dividend checks to their members. The rest are very closely held - like a private family corporation is. Calif had a few cases when casinos were first approved of tribal leadership voting out members left and right - who continue to have no recourse, state or federal.
The outcasts could band together and make their own tribes, (we had a group of 7 or 8 that tried that) but the existing tribes might challenge and that could get real expensive.