Or HaChaim on Deuteronomy 18:16/אור החיים על דברים י״ח:ט״ז

1 ככל אשר שאלת, "in accordance with all that you requested, etc." Moses may be telling the people that it is their own fault that not all of them have been elevated to the level of prophecy. At the time they asked G'd to make Moses their intermediary, i.e. their prophet, they had declined being prophets themselves. It was all because they had been afraid of the fact that prophecy brings in its wake a certain amount of fear and emotional pain. This is why they now need an outsider to tell them what they want to know about the future. This is the principal reason the Torah includes the reference to the revelation at Mount Sinai at this juncture.