I have heard of many googlers, who use Ubuntu on their macbooks. Besides that is an ability which is not a prerequisite for majority of the computer users. Look I am a Ubuntu (not on a macbook though) user myself, and being a developer love the freedom that it provides, but we have to remember that everybody's requirement of freedom is different, for vast majority of the users freedom means, freedom from spending hours to tinker with something to make it work, things should just work for them, and Steve provided that kind of freedom.