Considering how many systems haven't been Multi-Sited, I profess to some pessimistic scepticism that most companies would afford that kind of service. And for that matter, even then, local capability needs to be maintained. People trust parts of their cognitive sphere to your tooling. You'll cut them off from information they won't otherwise remember if your backend goes down.

Also, local internet services can be less reliable even if the cloud is reliable.

Lastly, the point about local data on the device misses the point. Take Tana's JSON for example. It's a giant data structure that's basically utterly opague to human inspection. Compare that with a Logseq file that I can find, search and read with a plain text editor.

Both of these come back to accessability as a core design theme. get access where you need, when you need it, with as little failure points between them as possible. SIngle-point cloud with no local storage and services is a failure edge. So is local data that is stored in human-opague databases. (but then, so is so localized data that there is no access via i.e. a web account).