(1) Justifying the existence of a system sounds like a value judgment
(2) There are useful databases that allow for reprdering data. The stated motivation for doublespend prevention is not because it is "technically necessary" (I dont think it is) but rather to prevent fraud, which is itself a form of "morality policing"
(3) The stated motivation for proof of work is to incentivize honesty, not to ensure the system is different from other BFT databases. Other BFT systems are permissioned. But one of the big problems with a permissioned monetary system is not technical but rather moral: dishonest parties might gain control of the system and use their power to allow some people to doublespend, i.e. to enable fraud. Having a pernissionless Proof of Work model incentivizes them to be honest instead. The choice to forego the permissioned route was not technically necessary (orher such systems ARE permissioned). It was a choice explicitly based on morality.