You need to be able to steer with the front wheels, so a simple differential like this wouldn't work. You need some additional complexity to support driving and

You need to be able to steer with the front wheels, so a simple differential like this wouldn't work. You need some additional complexity to support driving and steering with the same wheels (CV axles). It just took time for the technology to become cheaper, more compact, better engineered, and paired with smaller engines.