Why?
Because this doesn't fit into your paradigm?
Both Neil Armstrong and Buzz Aldrin have not denied their claims.
And for the record, for all of you progressives out there that would like us to find life somewhere out in the Universe, why do you instantly make fun of those who do?
You need to watch the Disclosure Project video and listen to all the military and scientific individuals who have come forward to tell their story. People that still ridicule others in the face of genuine eye witness accounts of back engineering and secrecy around military bases where ufos have buzzed them and knocked out all telemetry are legion.