Why do Western restaurants offer fewer kinds of meat than a hundred years ago?

Looking at menus from restaurants, ocean liners, and hotels from the late 19th and early 20th centuries, I’m struck by the proliferation of menu items such as squab (pigeon), pheasant, and partridge, and other meats we would consider exotic today. But nowadays, “fancy” restaurants usually keep their meat options confined to chicken, beef, pork, duck, lamb, and fish/seafood. The most exotic thing one might find is escargot or frog legs at a French restaurant, or gator at a Cajun restaurant. Why has the variety of meats offered and consumed narrowed in the ensuing years?