Leonard herself was surprised at the success of these numbers.
Originally phone sex services consisted of a managed network of dispatchers (live or automated) and erotic performers.
(This attitude still survives among some providers.) When public (mostly female) pressure forced the phone companies to stop providing this service to sex workers, a transition was made to a manual method: pre-paid blocks of time, 10, 30, 60 minutes, whatever the customer would pay for.
The incentives for providers were then reversed; rather than earning money from keeping the customer on the line (orgasm delayed), they earned more from bringing the caller to orgasm quickly, so as to move on rapidly to another call.
Performers would come to a studio where they received a cubicle, coaching, and cash incentives to keep callers on the line longer.