[hiq]

> without you ever having to pay server costs - i.e. for the person deploying the smart contract it can be much cheaper

That's just offloading the costs (or passing the costs down to the users), that's not a solution.

> it's the default way of writing blockchain applications

There's no default way of writing smart contracts, where does that come from? I've seen my share of smart contracts (tokens, stablecoins, NFTs) where one single address control everything, or where external approval is required for any interaction to happen. There's no "default" there.

Even if you manage to convince a bank or other financial institution to use a blockchain, they won't relinquish control over what they deploy there. There's just no incentive in favor of that, and so many against (regulations, complexity). But more to the point: "using blockchain" as a constraint doesn't change the incentives when it comes to interoperability.