You don't need to. It's installed on every new Mac. I've never actually tried to remove iLife from the Mac, because I actually use my computers for more than... actually, what DO people use computers for that iLife doesn't cover? And if they aren't using modern, powerful computers for music, video, multimedia tasks - why aren't they still using 486s with
32Mb RAM?
Well, let's see.
If you don't have the device, and the default is to offer the update anyway, with the option to ignore said update available one click away, anyone who does have the device but is unaware of the update is offered it - making sure they get new features, compatibility with new accessories and so forth.
If the default is not to offer it, then many people who have the iPod will not update it, and miss out, because they won't check or look.
Richard