You'd be amazed at how many of my customers don't realize the need for a firewall. Some of them became my customers because they did an "everything" install and put the box right on the net. I agree, that's just an absurd thing to do. The fact remains, they do do it.
So are support to try to build a systems that are idiot proof? I would say not... If someone neglect to lock their front door and is robbed, is that the builders fault because he didn't install automatic locking doors?
Firewalls is the best way to deal with network security.... and there no system configuration that we can do to change that fact...