Why would the passport agency need 5 more pieces of identification more than 20 years old?

I'm 33 years old and this will be my first passport. I got the pictures taken at the post office and provided all the IDs and original birth certificate

Source: http://www.us-passport-service-guide.com/why-would-the-passport-agency-need-5-more-pieces-of-identification-more-than-20-years-old.html

government passports united states passports online passports