In other words, standard contracts work just fine (without any lawyers involved) when everything goes to plan. It's the failure cases that matter, and it's not hard to imagine a compromised lock (or an entire company's locks if they're connected to the internet for access to the blockchain) that no longer respect the smart contract. So you're back to calling your lawyer to help sort out the mess.
The part they say quietly is that the ledger supersedes the law and legal framework, and that’s clearly not how governments and their legal frameworks work.
If you use a smart contract you don't need to maintain any sort of backend at all. Your infrastructure costs are basically zero because they're baked into the cost of using the contract, which is paid on every transaction. You also get interoperability for free without having to build out any sort of API layer.
Smart contracts are not the solution to all problems but I think they have some really interesting use cases.
I have heard several stories by now of renters being defrauded by fake landlords. A smart contract could actually help. Decentralized would mean everybody can check who owns a property, not just the owner of some obscure property database.
Isn't there a public ledger of property ownership? In any case, there could be.
In my country, merely transferring property rights costs a lot of money. I know a friend paid 20k just for officials to make the entry in their book.
Blockchain could easily replace that.
Or the "property officials" could have a key and people could verify with the smart contract that some transfer has been signed by the right key.