“Why did the bowling pins stop working?”/“Because they went on strike.”

A bowling riddle has been cited in print since at least 1984:
   
Q: Why did the bowling pins lie down?
A: Because they were on strike.
   
A slightly different version was printed in 1997:
 
Q: Why did the bowling pins stop working?
A: Because they went on strike.    
   
         
Google Books
The Zaniest Riddle Book in the World
By Joseph Rosenbloom
Illustrated by Sandy Hoffman
New York, N: Sterling Publishing COmpany, Inc.
1984
Pg. 108:
Why did the bowling pins lie down?
Because they were on strike.
     
Google Books
Multiplication and Division:
Reproducible skill builders and higher order thinking activities based on NCTM standards
By Brenda Opie, Lory Jackson and Douglas McAvinn
Nashville, TN: Incentive Publications
1995
Pg. 88:
WHY DID THE BOWLING PINS LIE DOWN? Because they were on strike.
   
29 November 1997, Seattle (WA) Times, “Raising Stars,” pg. D8:
Q. Why did the bowling pins stop working?
A. Because they went on strike.
 
Twitter
Jeff Murphy‏
@PintofStout
The jokes from my Laffy Taffy: 1- Why did the bowling pins stop working?; 2- Why do fish swim in schools?...
12:09 PM - 2 Nov 2009
   
Twitter
Joannah Seaborn‏
@jseaBORN_Cr8tiv
Laffy Taffy Joke #1 Why did the bowling Pins stop working?......Because they went on strike! SMH/LOL :D
11:47 AM - 9 Nov 2009
   
Google Books
August 2010, Boys’ Life, “Think & Grin,” pg, 52, col. 2:
Dawson: Why did the bowling pins stop working?
Lawson: Why?
Dawson: Because they went on strike!
Dawson Mauck, Detroit, Mich.
 
Reddit—Jokes
Why did the bowling pins stop working?
submitted January 30, 2013 by epml21
They went on strike!
 
Reddit—Dad Jokes
Why did the bowling pins stop working? (self.dadjokes)
submitted March 31, 2017 by I_Fart_Liquids
They went on strike.
 
Twitter
thankful dad jokes‏
@dadtellsjokes
Why did the bowling pins stop working?
ecause they went on strike.
10:15 PM - 13 Nov 2017