Official Statement: At launch, we offered two separate models of PLAYSTATION 3 to meet the diverse needs and interests of our PlayStation fan base. Initial retail demand in North America was upwards of ninety percent in favor of the 60GB sku, so we manufactured and shipped-in accordingly. Due to the overwhelming demand for the 60GB model from both retailers and consumers, we have ceased offering the 20GB model here in North America. In addition to the larger internal hard drive, the 60GB PlayStation 3 features added storage media slots and built-in Wi-Fi not found in the 20GB system. Based on retailer and consumer feedback, we have decided to focus our current efforts on the more popular 60GB model.
Now, if Microsoft could follow suite. We need everyone to have a HDD.