Why is the demand curve referred to as a marginal benefit curve?

The demand curve is referred as the marginal benefit curve because the amount that customers are willing to pay for the next unit of a good is equal to the marginal benefit expect to be received.

Explanation:

The marginal benefit is the value of one more unit of product or service. This marginal benefit can be referred as the maximum value that consumers are willing to pay for another unit of the service which is shown by the demand curve.