I chose happy for a reason :)
So the business is chasing profits. In the short term that means customers paying money - any will do (happy or unhappy).
But in the long term, happy is the key. Happy customers are the single biggest marketing tool you have. Happy customers promote and recommend you. Unhappy customers do the opposite (and are more effective at doing so.)
So, if the metric stops at Customers then you are greatly missing the long-term value. Since a good business is planning for the long term, not just right now, Happy customers I the correct metric.
Remember, you ultimately get what you measure (no more).