More jobs being destroyed than built means less money to spend by individuals, which means less profit, which means lower expectations, rinse repeat in a loop.
This is the deflation doom spiral, and the companies causing this cycle like most other problems think, this is a problem for next quarter; each time.
Sometimes making something cheaper to make, just means you make more with the same people as demand is elastic and price driven.
The other question is if you need less people ( less say for farming ) is there anything else these people can do ( ie work in factories ) - that depends on whether there is fundamentally enough tasks to go around.
If you look globally it's quite clear that even the basics - like clean water, enough food and decent housing hasn't been sorted. ie there is plenty of work still to do done.
Your reasoning also conflates the economic concepts of "demand" with "need". The two are quite different. The latter assumes there is some cross section of exchange that can happen between supply and demand, whereas with the cohort of people in need, they are anyone that could benefit but which no exchange is possible.
You speak about opportunity cost, but you also neglect distortions. The suggestions you make do not happen in a vacuum and we are at a point where the entire bottom rung of sequential careers is being removed. Sequential pipelines fail over time when the initial inputs go to zero; they fail on a lag but if you take the entire cycle as any competent engineer would during design, its clear.
If you look globally, water, food, and decent housing hasn't been sorted and won't be sorted because its more profitable to keep these industries captured and distributed as a narrow peak spinodally. For a clear example the SROs of the 50s and 60s.
People don't realize they are in the grip of runaway money-printing schemes, and when you replace people with machines in aggregate, the real economy shrinks proportionally. When it gets beyond a certain threshold you see violence because these are the exact same living conditions and dynamics that led to 1776, only its worse because of fiat currency.
There may be great need, but so long as there is no demand to incentivize change it will forever lay out of reach. Economics is not so easily tamed with the money-printer its filled with invisible pitfalls.
What's worse is many of my Socialist friends that want to make the world better neglect these things, and some of them are fairly intelligent but they are dogmatic when it comes to any mention of incentives as being too close to Capitalism. Neglect in these areas though leads to eventual collapse, which we are seeing in slow motion with the collapse of the birth rate. People don't have children if they lack the economic means to do so.
( a macro version of the rich exploiting the poor )
> People don't have children if they lack the economic means to do so.
Surely the very clear global trend is birth rate is inversely proportional to wealth - not the other way around.