Earlier quoted context omitted.
What is preventing Zeiss from paying higher salaries to mirror grinders, so that young people consider that career over alternatives?
Uncertain long-term career prospects that depend on a single employer. If you pay enough to make long-term prospects irrelevant, you may end up attracting the wrong kind of people. People who can't be trained do the job well enough, or people who will quit after earning enough. And you may end up losing your existing employees. They may quit if they don't get paid as much as the new hires, or they may FIRE if they do…
Also, it sounds like the entire premise is "people don't want to work because they're not being paid enough" which is enough of a good reason by itself.