I don’t know enough to have any real thoughts, but my understanding is that a NuShareholder need not own NuBits, and a holder of NuBits need not be a NuShareholder - so they separate
If Nu was a manufacturer of chicken feed, the owners (NuShareholders) would need a system to manage raw ingredients, production, personnel, payroll, IT, etc - all the things to run a factory
Such a system would not relate to the needs of the farmer (NuBit holder) who would need a system for ordering feed, dispensing the right quantity and making sure the chickens are fed at a certain time each day
So, why mix two unrelated systems?
There is also a security implication, in that if both NuShares and NuBits are in the same vehicle, and one crashes or is highjacked, then so is the other