What makes you think improvements in productivity will result in higher earnings for blue-collar workers? In reality relative productivity and pay have diverge

What makes you think improvements in productivity will result in higher earnings for blue-collar workers? In reality relative productivity and pay have diverged wildly since 1973: https://www.epi.org/productivity-pay-gap/ https://www.epi.org/productivity-pay-gap/ It seems like increases in productivity would only increase employment and pay if there are laws in place to make those things happen.