The rewards here aren't just cosmetic or meant to cheer you up; they're digital items or resources with real value in the game. You might find yourself winning something linked to your account (meaning it's yours alone), or you might find something you can sell and earn in-game. The beauty here is that the value of the rewards increases based on the difficulty of the challenge you win. The bigger the challenge and the bigger the reward.
So how do you win these rewards? Simply put there are several ways. The first and most obvious is by winning a match. If you're awesome and beat your opponent in a match, congratulations! The prize is in your pocket. But that's not all the game also motivates you to fulfill certain conditions or special challenges, and when you complete them, you earn additional rewards.
Imagine, instead of just playing and finishing so you play with your eyes on the prize. This isn't a small thing, because over time and these rewards help you further develop your game, buy new items, or even sell them if the game allows it, and earn more.
What I like about this system is that it keeps you motivated and focused at all times. Every match has meaning so every challenge has weight. It's not just entertainment and you can leave the game feeling like you've actually won something.