Why is there no "Grandma Burger" at A&W restaurants?

Nobody seems to know, but here's the petition to request one:

At the A&W fast food chain they have a variety of burgers.

Baby, Teen, Mama, Papa, Grandpa, and Uncle Burgers.

Where is the Grandma burger? Surely to complete the burger family a member of the immediate family holds a higher priority than an uncle?

VOTE TO GET A&W TO REPENT AGAINST THEIR EVIL WAYS AND CREATE A GRANDMA BURGER!

[ petitiononline.com/8883821/petition.html ]
[ scotthutcheson.typepad.com/scott_hutcheson/2006/12/the_teen_burger.html ]
[ links no longer exist ]

Actually, they did run a limited edition called the Grandma Burger which consisted of "a prime rib burger topped with caramelized onions and horseradish sauce". It was launched in early 2011 and discontinued the following year.
https://blogs.ubc.ca/andreawong/2011/03/24/aws-grandma-burger/

The Grandma Burger was a menu item part of the Burger Family that was only available in Canadian restaurants. Unlike other burgers, the meat in the patty consisted of prime rib beef. It was discontinued due to low sales.

https://allenandwright.fandom.com/wiki/Grandma_Burger