No busybox in android; that too is GPL software that Andy Rubin and the pre-Google Android people didn't want to ship. They actually hacked up a minimal "toolbox" to avoid shipping it. Sad, really.
It's just the standard fear. Shipping GPL code you didn't write means that you need to honor a license in ways you might not forsee. Some people view that as a scary risk and some don't. Rubin is firmly in the "GNU is for commies" camp. Shrug.