IIRC card counting relies on tracking which cards have been drawn and thus inferring which cards are remaining in the deck. Shuffling by hand is a tedious process, hence it is done only so often and this makes counting possible. With electric shuffling machines, shuffling becomes easier and is done more often. This, in turn, makes counting cards harder because the remaining deck never gets small enough for you to draw any useful conclusions about the remaining number of cards. In an online casino, you would have the same problem I guess ...