Because immediate visual feedback is more natural than having to imagine an operation in your head, it's the same logic for multiple cursors - where it's even harder to understand what "change this word" will actually change.

> why THAT of all things?

Because that's a fundamental improvement

There were a few blogs with more detailed explanations, not sure about Helix, but kakoune had it covered https://kakoune.org/why-kakoune/why-kakoune.html

> Kakoune tries hard to fix one of the big problems with the vi model: its lack of interactivity. Because of the verb followed by object grammar, vi changes are made in the dark, we don’t see their effect until the whole editing sentence is finished