Definitely this is undoubtedly an attempt by Apple to make the most of his  users  migrate to icloud , or at least overcome the resistance of those Who doesn’t use.

 Thus, the Cupertino embarked on an interesting initiative that they give an Snow Leopard update  in DVD to all registered users of Leopard and MobileMe service. The idea behind this initiative is that from this version, users are encouraged to make the jump toLeopard, and there to enjoy the softness of the cloud with icloud.

MacNN also adds an observation, that Apple did not include a flash drive instead of DVD to provide the updated Leao, since the DVD now seems outdated.