The voice acting

All the voices were probably in-house by people who worked in other capacities within the company, such as programmers or secretaries. Possibly to avoid the extra expense of paying real actors.

One such example are Space Ace and Dragon's Lair by legendary animator Don Bluth. All the voices were done by animators and people on the crew. Don Bluth himself was the voice of Borf and Singe the Dragon. However THESE people did a pretty good job.

I doubt it could be technological limitations, as Space Ace and Dragon's lair are 15-20 years older and did better. Even earlier games like Space Fury, whos voices were completely synthetic sounded better.

Another possibility is these games were made in other countries like Japan where English isnt their first language.

An unlikely possibility was they were purposely screwing with us. They made it this way on purpose as a joke.