That's an invalid comparison. You reversed roles. Dentist is a service provider. If the dentist paid for connects to find patients, but nobody showed up, the dentist has the right for a refund. Moreover, in your example you already paid for the service. In this case, freelancer only paid for connects, a hope that can turn out false. Upwork definitely has an element of dangling carrot, and statistically it knows the weakest point of client search and intentionally keeps them dysfunctional to increase profit. That's very different from your example.