The dealer's are beginning to get tired & more prone to mistakes.
Actually, there are also a few other reasons why this sometimes is true, but shouldn't be discussed openly on this board. The wrong people could be listening.
I think your latter explanation is what I am talking about, though I am not sure why it shouldn't be mentioned here, as I learned it from an AP blackjack book. But I'll assume you know better than I and go no further since you suggest it is best not discussed here.
