As players can take measures to lower the blackjack house edge, so can casinos. There are two standard ways they can achieve this.
The first one is simple; the faster blackjack rounds play, the more money the casino makes. That’s because the long-term house edge favors it. In the past, casinos shuffled blackjack cards every 20 hands, and the time required for this cost them precious money. Nowadays, brick-and-mortar casinos have incorporated shoes that automatically reshuffle the deck; the same thing happens online but through a random number generator.
The second way casinos optimize towards their edge is by monitoring how each game performs. For example, if a slot machine payouts more than it should, it is most likely to remove it. The same can happen with blackjack dealers making errors.