From my experience, the biggest reasons are not having to worry about the server, updates, things work out of the box because they are made for each other and h

From my experience, the biggest reasons are not having to worry about the server, updates, things work out of the box because they are made for each other and hosted stores usually have easier-to-understand admin panel. Everything offered in the package is already optimized for the primary purpose of the platform (filtering orders, clients, adding products etc.). If you compare that with say Drupal or Magento - there are a lots of things you need to add and configure additionally (=> time and money) and still there is a chance that modules will conflict or that something will become incompatible over time. The thing is that hosted shops work for clients only until they hit the ceiling - often they will require certain functionality that is simply not possible, and depending on how important it is they will have to switch again. Think custom workflows, fulfillment integration, specific payment processing or any other non-standard feature.