The market for plain vanilla calling cards is very competitive.
Prepaid calling cards eliminate the need to make collect calls, they erase the need to pay expensive surcharges for long distance calls made from hotels, and they usually provide the cheapest per-minute rates available.
Prepaid international calling cards usually provide the cheapest rates available.
When the evening bag evolved into the 18th century, it grew larger in size as carrying the emerging social symbols of fans, perfumes, calling cards and coins became more important.
Most people hear about them because they offer free business calling cards (you pay shipping).