The same way Deep Blue doesn't waste its time worrying about promoting pawns on the first move of the game - even if you give it the very long term (and not remotely "discounted") goal of winning the whole game.

Is this really true? My understanding is that Deep Blue's position evaluation function was determined by an analysis of a hundreds of thousands of games. Presumably it ranked openings which had a tendency to produce more promotion opportunities higher than openings which tended to produce fewer promotion opportunities (all else being equal and assuming promoting pawns correlates with wins).