He created it to explore communication between humans and machines. ELIZA simulated conversation by using very simple pattern matching and substitution that gave users an illusion of understanding – but it had no representation that could be considered really understanding what was being said by either party. Something you can easily discover by playing with it for a few minutes.
Fast forward to 1991, and Creative Labs was having amazing success with their SoundBlaster add-on sound cards. On the driver disks that came with the SoundBlaster, there were programs showing off different capabilities. One of these capabilities was voice generation. To show off the ability to voice synthesize text, Creative Labs included a little program called Dr. Sbaitso (SoundBlaster Acting Intelligent Text-to-Speech Operator).
You interacted with it like a pseudo-therapist; but you can clearly see the connections and similar pattern/substitution methods that Eliza used. I remember being wowed by it when I played with it for the first time – and experimented for hours with it. It quickly shows its limitations, but the speech synthesis was very good for the time.
It doesn’t hold the test of time, but it is pretty neat and you can even check it out here: