There is a maximum win limit. In this option, a limit is placed on the money you can win with the promo. For example, even if you have 100 free spins, you can win a maximum of 10 EUR/USD using them.
In other words, you win real money without making a deposit, but a limit is set for your winnings. The casino is losing a maximum of 10 EUR/USD from this promotion. However, there is no real loss as a large part of the people who signed up using the promotion will continue to play.