The reasons the graph is centered around 30s with a halo in 20s, 40s and 50s is the same reason the graph lacks "under 10" and "over 80".
It's just how humans work. We get born, have a period of growing up, gaining experience, then a productive period with big bold dreams, then settling, retirement and death.
I guess without the finger pointing the data would be so boring that it wouldn't warrant an article, so here we go.