Its about an educated and critical thinking public. A public that approaches everything with a critical eye is less susceptible to political pandering and more accepting of good science and evidence/data based laws. The average person doesn't know how to interpret a bar graph and has no clue what a good source of data looks like. Agreeing on a specific point, such as evolution, is just a symptom of the larger problem.

Sure: People who don't believe in evolution can taint those around them especially the young, which could cause those to not pursue scientific careers, setting back further progress in those fields and pushing forward the next discoveries in fields like cancer, life-lengthening, and other diseases. These "potential setbacks of breakthroughs" hurts society's quality of life.

You would be less likely to get an antibiotic-resistant infection in the future, because an understanding of evolution is necessary to understand how massive application of antibiotics can lead to more resistant bacteria in the future.

You would be more likely to survive a pandemic in the future because there would be more public support for research into how diseases evolve.

There would be less racial strife because more people would understand that the differences we see in people lie on a continuous genetic spectrum, not broken up in distinct "races."