“Why does mineral water that has ‘trickled through mountains for centuries’ have a ‘Use By’ date?”

“Why does mineral water that has ‘trickled through mountains for centuries’ have a ‘Use By’ date?” is a jocular line of unknown authorship. The question was listed with other “WHY” questions on the newsgroup alt.clearing.technology on May 24, 2002.
 
One answer to the question is that the bottle itself might degrade, contaminating the water after a certain period of time.
 
 
Google Groups: alt.clearing.technology
Jokes (fwd)
Homer Wilson Smith
5/24/02
(...)
Why does mineral water that ‘has trickled through mountains for centuries’ have a ‘use by’ date?
 
11 June 2002, Atlanta (GA) Journal-Constitution, “The Vent,” pg. D2:
Why does mineral water that has trickled through mountains for centuries have a “use by” date?
 
8 November 2002, The Sun (London, UK), “Scotcha! on Friday” by Sergei Platt, pg. 6:
Why does mineral water that “has trickled through mountains for centuries” have a use-by date?
   
Google Books
Spam Revisited
Compiled by Scott Horner  
Nashville, TN: Westview Publishing, Inc.
2004
Pg. 182:
Why does mineral water that ‘has trickled through mountains for centuries have a ‘use by’ date?
 
Google Books
Do Vegetarians Eat Animal Crackers? and Other Questions You Might Not ThinkTo Ask!
By Robert Bimler
Lulu Publishing (Lulu.com)
2008
Pg. 40:
Why does mineral water that ‘has trickled through the mountains for centuries’ have a ‘use by’ date?
 
Twitter
Saithilak‏
@saithilak
http://tinyurl.com/5h4cdt asks: Why does mineral water that ‘has trickled through mountains for centuries’ have a ‘use by’ date? Ans: Fi ...
3:18 AM - 23 Apr 2008
 
Twitter
MoCoDo‏
@MoCoDo
Why does mineral water that ‘has trickled through mountains for centuries’ have a ‘use by’ date? Huh??
9:15 AM - 2 Mar 2009
 
Google Books
Shuttlecocks, Polar Bears and Noodle Soup - the Complete Edition
By Stu Wilkie
Lulu Publishing (Lulu.com)
2010
Pg. 67:
Why does mineral water that has trickled through mountains for centuries have a use by date?
 
Quora
Why does mineral water have a ‘use by’ date?
Martino Ciresa
Martino Ciresa, studied at University of Trento
Written 7 Aug 2014
I guess it does because it is contained in a plastic bottle that degrades over time, releasing part of its composition into the water.
 
Twitter
Bill Murray‏
@BiIIMurray
Why does mineral water that has “trickled through mountains for centuries” have a “Use By” date?
2:30 PM - 20 Mar 2017