7th rankedAPAC VOC commented
This is as per the Apple Human Interface Guidelines. See https://developer.apple.com/library/ios/documentation/userexperience/conceptual/MobileHIG/Branding.html#//apple_ref/doc/uid/TP40006556-CH60-SW1 - specifically "Resist the temptation to display your logo throughout the app." Users enter the app from the app icon, or from the multitasking screen which shows the icon and name, so are unlikely to be confused about which app they are in.
If we place the logo in the nav bar (on iPhone - iPad we actually do this all over the place), there is no room for the navbar content.