“Why do cannibals go to the movies alone?”/“No outside food is allowed.”

A cannibal riddle was posted on Reddit—Jokes on March 2, 2017:
   
Q: Why do cannibals go to the movies alone?
A: No outside food is allowed.
 
Forms of the joke had been posted earlier. “How do cannibals feel when they take a date to the movies and see the ‘no outside food’ sign?” was posted on Twitter on November 28, 2011. “‘No outside food allowed’ is probably why you don’t see many cannibals at the movies” was posted on Twitter on August 21, 2015.
   
     
Twitter
Tom Coletta‏
@tomcoletta
How do cannibals feel when they take a date to the movies and see the “no outside food” sign?
1:38 PM - 28 Nov 2011
     
Twitter
(((Mike Blejer)))‏
@MikeBlejer
“No outside food allowed” is probably why you don’t see many cannibals at the movies.
3:20 PM - 21 Aug 2015
 
Twitter
Dan Fitzpatrick‏
@DannyFitz1020
Cannibals only ever go to the movies alone, since most theaters don’t allow outside food.
5:53 PM - 28 Sep 2015
 
Twitter
Barbara Holm‏
@barbara_holm
It’s hard to tell if a cannibal at the movies brought in any outside food.
4:25 PM - 9 Jan 2016 from Portland, OR
 
Twitter
Mr. Sweet Escape‏
@zslambert92
When the movies tells you no outside food or drink but your a cannibal so everyone is…
5:17 PM - 21 Aug 2016
 
Reddit—Jokes
Why do cannibals go to the movies alone?
submitted March 2, 2017 by BearlyCompentent
No outside food.
 
Twitter
Meaganvictordc‏
@naimatamians
Why do cannibals go to the movies alone? No outside food. #ohmygod
4:41 PM - 2 Mar 2017