Quite often the AI guesses accurately and you save the time you'd have spent crafting the perfect prompt. Recently, my PM shared a nigh-on incompressible hand-scribbled diagram on Slack (which, in fairness, was more or less a joke). I uploaded it to Gemini with the prompt "WTF does this diagram mean?". Even without a shred of context, it figured out that it was some kind of product feature matrix and produced a perfect three paragraph summary.
I've never really seen the value in the planning phase as you're free to just throw away whatever the AI produces and try again with a different prompt. That said, I don't pay for my tokens at work. Is planning perhaps useful as a way of reducing total token usage?
This could simply be a matter of style however.