Card counting is illegal and I have been hearing about this but I haven't really seen it in practice...
Where did you get this information? If you count cards on your own, without the help of accomplices or devices, then from the point of view of the law, your activity is absolutely legitimate. This casino considers card counting illegal, as it increases the player's chances of winning, which leads to losses for the casino.
yeah the casino's eye will be at your side whenever they see advantages from you, they seen it as illegal but technically if there's no accomplices or any additional devices there's nothing but just a manual suspicion that the house owner can use agaisnt you, though if chances that you can simply hide whatever strategy you are using and not to exposed it you can earn decently without a trace it's doable but again casino is a business they always find ways to secure their money.