> Why not? The WASM approach the OP is suggesting works entirely locally, the web is simply pushing client code to your browser
Because "the web is simply pushing client code to your browser". Untrusted code. Which may violate the confidentiality of you document.
I still don't get it why companies which deal with "confidential information" are very happy to put those documents in the cloud. But ... it is their data and they decide what to do with it.
I think you're still misunderstanding. The documents don't need to be "in the cloud", the WASM in your browser can operate on them locally.
Is the WASM "untrusted"? Sure, I guess, all code you haven't written yourself is "untrusted" by default. Why would a native application shipped via CD or download be any more "trusted"?
Why not? The WASM approach the OP is suggesting works entirely locally, the web is simply pushing client code to your browser.