Card counting can still work in brick-and-mortar casinos, but its effectiveness has been reduced by various countermeasures. Casinos now use automatic shuffling machines, multiple decks, and shuffle the cards more often to make counting less reliable. They also monitor players closely for unusual betting patterns that might signal card counting and may ask suspected counters to leave. While card counting isn't illegal, it's difficult to pull off successfully due to these precautions, and even skilled counters only gain a slight advantage, usually around 1%.