To be fair, a patty sandwich of any type (be it hamburgers, chicken sandwich, beans, or any kind of imitation meat) is going to be similarly labor intensive and time consuming if one had to make the patty and bread oneself rather than being able to just buy them. I'm sure traditional recipes for most cultures can be made similarly convenient if probably somewhat different from their original form, if demand exists for them to be premade and sold that way. There's a specialty grocery store very close to my home that specializes in Indian food, tho also has some international foods from other places too, and it's freezer section has all sorts of Indian dishes done up as tv dinners, or premade frozen samosas of various flavors one just has to fry in a pan for a few minutes, among other things.