You are assuming that you'll always have the time and energy to determine what you need at the moment you need it, which doesn't really sound true.

You're also assuming that there are no negatives to saying what you want compared to just acting on things, but since the beginning of computing many people have proven this wrong time and again. I suggest you read about HCI as a research field and its history, it doesn't take much to realise how limited the average HNer's understanding of UI/UX design is, and how far current LLMs are from the skills required to be able to carefully design an app for productive human use.