You just popped the CD in and the program on it came up. A few years before that, the average computer was still booting to a command prompt. For non-hackers, a

You just popped the CD in and the program on it came up. A few years before that, the average computer was still booting to a command prompt. For non-hackers, auto-run was amazing. And since then, it has worked as intended billions and billions of times. Some microscopic fraction of those have resulted in a virus, rootkit, or other issue. Just because something bad can happen in a small minority of case doesn't mean a feature is a stupid idea.