Humility can be so important for making society run well because on the micro level, humility is what makes us say "you know what? It is a good idea for me to be quiet in libraries."
I think that many people are stuck in the teenage mindset of "who cares, I'll do whatever I want" which, despite being an important stage of psychological development, is realy selfish and annoying- and can be super destructive to society if carried into adulthood.
It's ok for teenagers to go through this stage of new independence, which sometimes goes into the "screw you" mindset, but only when there are adults who can put them back in line. Without them, society is screwed...
Follow certain unspoken rules of society like being quiet in libraries doesn't necessarily benefit ourselves, but it does benefit others. And if everyone followed this unspoken rule to be quiet in libraries, we would one day benefit from it ourselves.