You're presuming people know what they're doing. If someone clicks a bunch of boxes and things break, they might not know what boxes they checked/unchecked, they might not know how to get back to that window again (which menu item was it again? ).

If you think users aren't that stupid, you're wrong, they are that stupid. If you think people should not use the Internet if they don't understand that much, then you're suggesting kicking a large chunk of the population off the Internet. If you work in IT, kicking a lot of people off the Internet is a surefire way to reduce your industry's size.