>Many factories will use bar feeders to run their machines overnight, but going further with automation doesn’t get enough return on investment.

As a rule, yes, but I say it depends on how you measure ROE and what that human costs.

In situations where there's a collective agreement in place and you have to pay that labourer $50K/year + benefits (NTTAWWT), you get more wiggle room to make your case for retooling.

Another case is when I've worked for bigger manufacturers where there were some of us on site just in case we were needed and our salaries were part of facilities overhead.

We were paid no matter what and could do what we liked as long as production was running smoothly and our minor, secondary duties were being handled. In this time (~4hr/day) we could scheme or tinker to our heart's content.

Jobber shops (a.k.a. the real world) were a different matter ...