Probably because of the 'provide the keys' and not sue for any anti-circumvention tech in the GPL v3. The anti-tivo provision. Not sure if it applies to standalone system utilities, but I bet it is an internal blanket ban on the GPL v3.

Apple is very fond of locking down their hardware. Google took a very strong stance against the AGPL-even banning it from their own public code repo service before they shut it down.