dealing blackjack

Why, when it comes to playing certain cards blackjack online casinos a dealer about 2?
I thought it was blackjack 2 cards each? The casino also has a big advantage is only 1 card I also understand how to win more often when you set holdings less than 5 pounds?
Well, I've always been the dealer for 2 cards. Not just one.
Live Dealer monica dealing a game of Live Blackjack at Black Orchid Casino