Games that implement monetization often use monetization in an aggressive manner, either by forcing the player to watch ads with the option of paying to go ad-free or by making it a requirement to access certain content. This type of implementation essentially takes the player hostage and makes them feel impatient, disconnected from the experience, and cynical towards the game creators.
By offering additional rewards or currency the player can access elsewhere in the game in exchange for watching an ad, the developer is giving the player a choice, both with positive outcomes. One, the player can refuse the offer and continue playing the game. Two, the player can watch the ad because of the in-game incentive, and may watch more ads in the future because of the positive reinforcement and freedom of choice. The experience of watching ads isn’t forced and doesn’t require anything from the player. Instead of the player making the compromise, the developer is the one making the compromise, but one that is beneficial to them in the return on positive reputation while theoretically getting similar monetization results.
Crossy Road Edit
Crossy Road never requires the player to watch ads, and uses this exact system of monetization. The player can earn extra coins by watching an ad, which they can use to purchase new characters. The coins can be earned elsewhere in the game, but as the sole resource in the game, the player is motivated to earn more each opportunity they get. The game has no currency store either, so ads are its only online form of monetization (they do have a merchandise store, though). The player has the choice to play the game as long as they want without ads, but is likely to watch an ad if they wish to earn characters as fast as possible.