Like you said, they're trying to get people hooked.
But if AI isn't any useful to people in the first place, this goes nowhere and they're still stuck with a low/decreasing amount of users.
Also, from a UX perspective, I feel an autocomplete-based UI encourages me to make sure the thing “I’m saying” is actually what I mean to say - ie, to not implicitly trust LLM hallucinations.
LLM-based generative text everywhere, in every app, could be useful, very straightforwardly integrated at an OS level into all text controls, something MS is well-poised to do, and “Copilot” a very good brand for that. (And I would be shocked if Apple and Google aren’t working on the same.)
That said, that’s almost certainly Microsoft’s short-term strategy until then! And probably part of why Apple made their sudden priority shift towards LLM features.
MSFT stock pumps hard for the next few years.