Does Jack in the Box put soy-based meat products in their tacos?!
Most places have a seasoning base which has spices, salt, flavourings, binders and extenders, soya protein is often used it expands and makes the filling more dense and like a thickener traps the liquids and fat in the meat filling. That is what Taco Bell is saying in there commercials regarding there beef filling, if you buy a packet of taco seasoning at the grocery store, read the ingredients and you will see the say things.
Back in the 70's when there were shortages and things, ground beef mixed with soy extenders was sold in supermarkets.
What do you think Bocca burgers and other vegan/vegetarian meat substitutes are made from??