McDonalds has lobster rolls in NE during the summer months. Same idea. Although, admittedly[:I] I tried a lobster roll from McDonalds.
so, maybe, it’s for the tourists, who say, "hey, what the heck – I haven’t the time to stop at a real place while passing by chicago at 70MPH."
They had NY pizza in NYC, too.
Serioulsy, though, I think it’s just another way the local FF joint can appear to be linked to the local flavor.