I explain all about the cut card effect in my blackjack appendix 10. The reason house edge statistics are based on a non-cut card game is likely out of tradition and mathematical simplicity. However you make a good point that it would be more accurate to inflate the house edge figures to account for the cut card. Yet I am still going to stick to basing my house edge figures on the first hand of a freshly shuffled deck. Blackjack is hard enough to analyze without worrying about the cut card effect all the time.