The incidence of appendicitis is highest among adolescents and young adults (13–40 years of age) source (World Journal of Surgery)
Since the disease has a fatality rate of 0.30 - 0.37% Source: (Postgraduate Medical Journal) it should have long ago disapeared via Darwinian mechanisms. The appendix has no known beneficial function and yet kills those at breeding age.
Observation: This may be too hypothetical. Suggestion: delete ?