“The dinosaurs became extinct because they didn't have a space program. And if we become extinct because we don't have a space program, it'll serve us right!”

Source: The Sky Is Not the Limit: Adventures of an Urban Astrophysicist

In a Reddit IAmA. http://www.reddit.com/r/IAmA/comments/r62jp/iama_nasa_astronaut_that_recently_returned_to/c437ubd (2012)
An earlier similar quotation can be found in:
The dinosaurs became extinct because they didn't have a space program. And if we become extinct because we don't have a space program, it'll serve us right!
By Larry Niven As quoted by Arthur C. Clarke in "Meeting of the Minds : Buzz Aldrin Visits Arthur C. Clarke" by Andrew Chaikin (27 February 2001) http://web.archive.org/web/20010302082528/http://www.space.com/peopleinterviews/aldrin_clarke_010227.html

The Transhumanism Handbook, 2019

Review of “Eyes of Amber”, by Joan D. Vinge (as anthologized in New Women of Wonder, edited by Pamela Sargent http://jamesdavisnicoll.com/review/yet-more-sf-about-women-by-women, 2015
2010s
Context: There’s a rule I used to call The Niven Rule but which I just now have decided to call the Rusting Bridges rule. It came to me after reading Niven’s “All The Bridges Rusting.” In this story, humans have by the early 21st century explored the Solar System and sent not just one but two crewed ships to Alpha Centauri … despite which the characters moan endlessly about the dire state of the space program. “Eyes of Amber” would be another example of the Rusting Bridges [Rule]: No matter how much the space program you actually have has achieved, whether it’s first contact with aliens or trips to nearby stars, it can never have achieved as much as the space programs you can imagine would have achieved in its place, given that imaginary programs aren’t limited by issues of politics, funding, or engineering.

On the dangers and importance of the mission of going to the moon in "Gemini : A Personal Account of Man's Venture Into Space (1968) by Virgil I. Grissom
Context: If we die we want people to accept it. We are in a risky business, and we hope that if anything happens to us, it will not delay the program. The conquest of space is worth the risk of life. Our God-given curiosity will force us to go there ourselves because in the final analysis, only man can fully evaluate the moon in terms understandable to other men.

"Dinosaur Renaissance", Scientific American 232, no. 4 (April 1975), 58—78
Dinosaur Renaissance (1975)

Interview with Al Jazeera (27 March 2007)
Interviews

Indonesia could go 'extinct' if I lose election: Prabowo https://www.thejakartapost.com/news/2018/12/18/indonesia-could-go-extinct-if-i-lose-election-prabowo.html The Jakarta Post (December 18, 2018)

2000s, 2003, Columbia space shuttle disaster (February 2003)