The average for tens of thousands of companies in the US is not in the 30's, it is 42 years. Taiwan Semiconductor was started by Morris Chang in his 50's. The reason for this is that startups need extensive experience, some of that experience comes from industry and companies the founders have worked with. With a deep knowledge of the field thay are in these founders can apply this knowledge to create new companies and discover new opportunities.
Even in government this is the case. In the recent appointments nominees selected by the incoming Republican DJT administration for Health and Human Services, Interior Secretary, Department of Energy, Homeland Security, had decades of experience in their field, some were governors of energy rich states. Another characteristic that comes with experience is the energy and aptitude for the job that they can bring.