It's not just that it's how it's worked out in the past, but it's that it continues to work out that way every month in the present. Roughly 24% of jobs are permanently replaced in the US every year (which I found very surprising)
"Researchers’ estimates on the scale of threatened jobs over the next decade or two range from 9 to 47 percent. For context, every 3 months about 6 percent of jobs in the economy are destroyed by shrinking or closing businesses, while a slightly larger percentage of jobs are added— resulting in rising employment and a roughly constant unemployment rate. The economy has repeatedly proven itself capable of handling this scale of change, although it would depend on how rapidly the changes happen and how concentrated the losses are in specific occupations that are hard to shift from."