system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is card counting illegal in casinos? Isn't it just a skill that not everyone has, how would they even know?
gpt
It's not "illegal" it's just frowned upon and will likely get you kicked out and banned.  
Casinos are businesses, and their goal is to make money, not lose it. So anyone who wins too much is going to look suspicious, and eventually they are going to be asked to leave, regardless of if you just got really lucky or had some kind of strategy to help you win more often.