Comment by bluGill

Because automation is expensive. It pays off in volume. A skilled human can often build a single widget faster than an engineer can write the automation for the robots (because a skilled human will see parts that don't fit and "file to fit" while the robot demands more effort to double check all that). When you only need 10, the program is faster to write, but you still need to pay for the robots and they are expensive (often $million each, while the human is only a few thousand for his time)

Of course there are a lot variables in the above. As time goes one automation gets better. You can buy cheap robots for some common operations, and a good engineer with good CAD can run various automated analysis to ensure fit and then export to the robot and build even a single part cheaper than the human - amortizing the cost of the robot over thousands of different single parts made this way. However as the widget gets more complex you reach the point where humans are needed. In some cases you just have humans to take the parts off of one machine and put them into the next, but it is still humans. We can automate even that, but often the robot to do that would cost more than a human for 10 years.