Any smart contract could also be implemented as a regular program dealing with numbers instead of cryptocoins. And transparency isn't a real benefit either, ass

Any smart contract could also be implemented as a regular program dealing with numbers instead of cryptocoins. And transparency isn't a real benefit either, assuming the centralized server makes all transactions public. The issues crypto can solve are 1) the government/bank can't steal your money, 2) the government/bank can't hide corrupt transfers, and 3) you don't need permission from the government/bank to exchange cryptocoins. If the government/bank wasn't a bureaucratic mess it could solve all of these issues centrally. Decentralization is good because it's hard to create a central agency without it turning into a bureaucratic mess.