That is primarily because they couldn't. But note the distinct lack of hardware expansion on early models: [ http://folklore.org/StoryView.py?story=Diagnostic_

That is primarily because they couldn't. But note the distinct lack of hardware expansion on early models: [ http://folklore.org/StoryView.py?story=Diagnostic_Port.txt http://folklore.org/StoryView.py?story=Diagnostic_Port.txt ].