@Dark_Shiki
While that would simplify the shopping experience, it would also limit the abilities of JAST USA, making it less independent. Your idea is similar to merging audible.com into amazon.com. There are pros and cons to this method.
Keeping JAST USA independent of J-List allows JAST USA to be more flexible, and change based on its customs' needs faster than if under the J-List umbrella, since game sales for J-List is only 10% of its total, but 100% of JAST USA. For example, the current JAST USA website upgrade was made possible because its not tied to the development of J-List, and vice versa.
Also, not all physical package sales come from J-List. About 30% of package sales come from other sources, like rightstuf.com, faku.com and amazon.com. JAST USA has an intensive to find system methods that benefit these customers as well, while J-List has less motivation to assist its competitors. JAST USA's goal is to localize and distribute visual novels to as many people as possible without going into the red, while J-List's goal is to make money.
Just my two cents ^_^