The optimal fit doesn't remain static.

The reason for all of [job hopping, fluid labor markets, bankruptcy, startup formation, inflation] is because the world doesn't stay the same. Desires change. New technologies are invented. Resources get depleted, and substitutes need to be found. Bottlenecks emerge. Old people die, and young people are born.

Changing wages and periodic layoffs are ways of adapting the jobs that people do to the new realities of which jobs need to be done.