The AppIcon and LaunchImage assets in asset catalog respond to your project configuration.
If you have iOS SDK 7.1 and deployment target of 7.0, you do not need any iOS 6 resources, because your project will not run on iOS 6 operating system. Why would you waste application size, when resources are not used ever?
Same goes for iPhone and iPad. You probably selected your project as iPhone only, so you do not need iPad resources.
If you selected deployment target 7.0, that means that the device needs at least iOS 7.0 installed for your application to run. Because iOS 7 only runs on Retina phones (iPhone 4 and newer), you do not need resources for anything else except Retina (which have the @2x in the name).
You do need resources for normal devices, if you are running on the iPad, because iPad 2 and iPad Mini do not have Retina.
Hope this explains it.