I am most definitely not an expert on food, let alone vegan food (let alone mock meats aka: faux meat, meat analog, fake meat), but I've eaten a good amount of meat substitutes--for better or for worse--so I want to talk a little about how and why you see so many mock meats in vegan restaurants.
Mostly you see them in forms familiar to all of us, the most familiar of all being the veggie burger. Ah, the veggie burger! I've had some great ones over the years and some pretty awful ones (I'm thinking of the ones they served at my high school in Virginia that were stuck to the buns and when you tried to take it apart to put in some ketchup the whole thing would fall apart).
Which brings me to how non-vegans deal with these fake meats. In yesterday's NY Times there was a review of Candle 79 by Frank Bruni where he mentions that, "...I'm convinced that many vegans are antsy about what they're missing." Referring of course to the many seemingly meat-based dishes that are on vegetarian menus. From the face of it, it seems like he's right. There is fake chicken on the menu so of course we all really want it to taste like chicken....right? The quick answer of course is no. (A hard NO!). We want good taste like everybody else and a multitude of textures and flavors from vegetables, grains and fake meats alike. Mock meats represent something different from a normal tofu stir-fry or whatever it is people are cooking.
The persistence of fake meat on the menus of vegan restaurants is more a product of the fact that vegan cuisine hasn't been around that long as it is named, and so a culture of dishes and menus and good-ole-standbys just has not come up yet (the word vegan was coined in 1944 and so for the purposes of this conversation and really for all intents and purposes, modern western veganism started then). We don't have a chicken piccata or pot roast or turkey dinner. Restaurants are still almost working backwards taking the chicken piccata and veganizing it, instead of starting with a list of vegetables and spices and grains and herbs and oils and going from there.
Obviously it's just much easier to make a version of something people already know than it is to make say, sauteed wheat gluten in lemon sauce. Mostly because that sounds kinda gross, even though I'm sure it could taste pretty good. (You will find wheat gluten named on the menus of Chinese restaurants and others, but I'm more specifically talking about American and/or western attitudes towards mock meats).
So what it boils down to is that we need new words to describe these things. Bruni said in his article (referring to a vegan reuben sandwich), "...sort of makes you wonder why it doesn't just take a different name, like an Irving or a Bernard." Now vegan or non-vegan alike, I don't think anybody wants to eat a Bernard (with no offense meant to anyone named Bernard). However it really is incorrect to say "mock" meat or faux or whatever as it is a real thing; it's wheat gluten. It's real seitan. We use these words because we just don't know what else to call it yet.
There are some fake meats that use that nomenclature just for practical reasons. The case in point is our old friend the veggie burger. Most veggie burgers taste nothing like a cow meat hamburger, but we use that name more for convenience sake so that we can describe the shape of what we're eating. It's a sandwich certainly, but burger is a good word to describe the shape made from taking an ingredient and making it in that specific form. It's almost a processed food (unlike ribs or legs which are literally ribs and legs) and so to make a burger out of beef or beans you still have to start with ingredients and process it in different ways to make a shape and so we end up with that word burger to describe it, which probably will not go away because it's just too damn convenient (and because most people don't want to eat something called a "bean patty").
But a chicken breast is a chicken breast and a fake version of that will pretty much never live up to the real thing when it comes to taste or texture (not to say it tastes better specifically, but the flavor and texture is different) and so we shouldn't even call it that. It's not the taste of meat and it shouldn't try to be a substitute; it's wheat gluten or soy that's boiled or baked and has a chewiness and texture that's quite good on it's own. There are bad fake meats much like there are bad animal meats, but mock meats haven't been around long enough in mainstream American culture to prove themselves as a fair substitute. We need more experimentation and more recipes to move forward vegan cuisine in a way that's uniquely our own, so sometime in the future we will no longer need the words mock, faux or fake. What I'm saying is we need ourselves some new words. It's going to take time as a vegan cuisine evolves and restaurants get better and recipes get better but sooner or later a seitan sandwich will be as normal as, well, a reuben.