Except, they did.
Manual labour is way way down from where it was. And skilled trades are a much smaller portion of the population than in past.
That was fine in the past. There was new frontiers in industry, service and other sectors to absorb the surplus labour.
Automation is going to affect everything. There will be no new sectors. We will not require a significant portion of the population to put in full-time hours in order to get everything done.
How about the new sectors of developers, programmers, maintenance, service, marketing, accountancy etc etc for these automation companies.
My point is, we're moving up as humanity, jobs will always follow. Just look at last 75 years where machination and automation have already taken large chunks of traditional jobs.
With less people in factories and working the land, Hell... even the Female population joining in; we managed to increase desk jobs all across the board (better/healthier) , inflated our entertainment industry by an enormous ammount (Radio -> TV -> MTV -> youtube), created an incredible amount of technical progress (engineering jobs), created the internet (programmers), created an enormous market in luxury goods, Built many more buildings and structures then ever before, Tourism has skyrocketed etc etc.... progress.
In the Netherlands we knew worker shortage for about 65 of these 75 years (high unemployment was mainly during the peaks of a number of crisis), for the rest it increased our living standard almost unimaginably, made jobs healthier/better, increased our pay and vacation days and lowered our weekly working hours.
IMO it just frees us up for "better"/other things.
increase desk jobs .. inflated our entertainment industry .. engineering jobs .. programmers .. enormous market in luxury goods .. Built many more buildings and structures
That's my point. All kinds of new areas to exploit. What happens when those are automated? Because they will be. Desk jobs, service, even construction and programming will be mostly handled by automation.
As a whole, we have always struggled with the problem of overproduction. It is soon going to get much worse, and will be unsustainable with our current system.
Seriously, what do you think the average meathead from highschool is going to be doing for a living in 40-50 years, that couldn't be better done through automation?
The idea of everyone being employed full-time is going to become a relic of the past. If we don't accept that and begin a transition, then things are going to get dangerous as jobs dry up and wealth disparity continues to grow.
Just like dem tractors took away our farming jobs and dem fancypants automobiles took away our charoteering jobs!