The reason for the rule is to prevent collusion or "soft play" between players, although in most cases a player checking back the nuts often does so without realizing he or she has an unbeatable hand.
Why is checking the nuts illegal?
Most people view checking the nuts as unethical behavior or soft-play. It's considered disingenuous if a person holds the nuts and checks. While not technically illegal in most cases, it is almost always considered wrong.
Do you have to bet on the river if you have the nuts?
As someone else have said, its a rule in many live tournaments, and its only about a situation, where you are closing action and have the pure nuts. In this situation there is no reason to not bet or raise, so if you fail to do so, it is either an honest mistake, or because you are trying to help your opponent.
What are the nuts in poker rules?
In poker, the nut hand (or the nuts) is the strongest possible hand in a given situation. The second-nut hand or third-nut hand (and so on) may refer to the second and third best possible hands.
What does nutted mean in poker?
A hand that is not the literal nuts, but close enough in strength to be considered nutted. For example, a flopped set is frequently considered to be a nutted hand. Nodelock Nosebleeds Nut flush Nut flush draw Nuts Odds Offsuit Omaha On the button.
Should you bet on the river?
There are only two real reasons to bet on the river. The first is to either to force an opponent off the hand with what is effectively a bluff if you think that you can get them to fold. The second is to bet on the river for value because you are confident you have the best hand.