While I personally wouldn't go as far as "Society profits immensely from their contribution", these types business people do serve an important function in the economy.

Much like traditional middle-men sellers, commodity speculators, insurance providers, and the like, domain name re-sellers take on the risk that no one else are willing to bear at some particular time (that the domain they're "squatting" could be worth nothing in X years). If and when the domains they're "squatting" later on become more valuable, either through their own direct efforts, or by re-selling them to other parties that can make better use of them, then the profits they make from such transactions are justified for the aforementioned risks they bore.