There are different marketing programs including deposit or welcome bonuses for you to choose and join. Imagine that if the wager requirement is 1x, in the perspective of a business entrepreneur,  it's awareness of possible considerable users can claim it. This means the company will have to pay significant amount of money for it. Oppositely, if the wager requirement is higher than 1x, there will be less users can claim it.

Now, you can think of two opposite scenarios and possible oppossite available offers for users too: 1x wager requirement and small reward to claim; 2x or higher wager requirement and bigger reward to claim. As said, there are opposite probabilities of succeed at the end with different wager requirements.