> now everyone but the house is guaranteed to lose.

Gambling is about more than making money. Most gamblers do not expect to win, they do it because its entertaining. Paying $1 for the opportunity to participate in the coin flip is something many people are happy to do. Negative EV does not equal losing because you forgot to include the entertainment value.

Scams involve deception. There is no deception in a business that is upfront about taking a fee to match gamblers.