What the hell are you talking about? You are absolutely not allowed to bet on whatever you'd like with another individual. Depending on what you're betting on (for example, the price of a stock or the throw of a card), it falls under varying different regimes. This is highly regulated and has been for most of the whole of human history.

Yes, there are de minimis exceptions. Your office NCAA pool, for example, is often legal, but it has nothing to do with what we're talking about and is also irrelevant to a business facilitating it via 18 U.S.C. § 1955.