Surge fares are totally unpredictable and random. Who is going to take Uber to Narita when you don't know if the fare will be 25,000 yen or 75,000 yen. To Haneda 8,000 or 25,000. Especially since you don't know till the last minute when it's too late to change plans. I don't even think about using them to go anywhere when a schedule is involved.