system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What is "counting cards," why do casinos ban you for it, and how do they know you're doing it?
gpt
Why do they ban you:  so they make more money by not giving some of it to you.

How do they know you're doing it?  By the way you bet.  Counting isn't the hard part, the hard part is making bets to take advantage of the fact you are counting, while appearing as though you're not doing that.

In order to maximize your winnings you want to bet the minimum when you have a low chance of winning, and bet the maximum when you have a high one so that you reduce your losses and maximize your gains.

But if you bet small, small, small, small, HUGE, HUGE, small, small, small, small, small, small, etc it makes it very obvious what you're doing.

That's why professional counters these days never work alone and always work in teams where the person betting and the person counting aren't the same person.