The problem is that those people are only employed for a short time in respect to each machine.
For example: 2 assembly line workera are employed for 40 hrs / 50 wks a year at $6/hr = $12,000 / yr * 2 = $24,000. A robot can be built for $48,000 with $6,000 / yr maintenance. Over 3 years the robot has paid for itself. It only employed a design engineer for 4 weeks to design it, a crew of 2 for 1 week to build it and on average one tech for at most 1 week to maintain it.
The robot company needs to sell 50 robots to keep everyone working all the time, so that's 100 line workers it can replace while only employing 4 people plus a few support staff.
I call that a net loss.
I've been in manufacturing for years and have seen it happen too many times. It's not new but a fact of life. As an IT guy I've personally created systems that have replaced 10 people without spending anything other then 3 months of my time, simply by automating data entry. Doing that saved a company from going under, but that's 10 people that will not be rehired.
Employment is down because of technology. Systems are getting better, more complex and more reliable, so the trend will only increase.