That doesn't make much sense. There's APIs now, and API intermediaries line Zapier, IFTTT. AWS APIs are backwards compatible, as I'm sure is the case for whatever US government APIs there are.
If I write some dip shit application and host it on my server, and you want to write an application that interops with mine, I can change my API (or the data itself) under your nose. You have no formal guarantees. Smart contracts make guarantees about what can change and what can't change.
Ethereum makes no such guarantee after the introduction of delegatecall, where it's possible to replace one smart contract implementation with another.
True. I'm curious what this sort of hit replacement would look like in practice. But, you can't add it in after the fact, so you at least have the option of writing contracts that give you the formal guarantee.