That is how you dent the "premium" perception you have built over several decades. You don't want your users buying $1500 phones and then having to search the web for solutions and pick up $5 converters off Amazon. You could have easily included one in the box.

I was wondering about those while watching the keynote, but now that I see the price of 10$ I think most people would rather buy a cheap USBC charger at 10$ instead of an adapter?