Personally, I think that the reason for this is because the thought of preparing it scares a lot of people, given its color and connotations. Which is such a shame really as its appearance bellies its great taste and even just the idea of eating it should not be a hindrance to actually eating it. After all, beef or ox tongue is nutritious, meaty, and errr, beefy. It also has great texture and comes with a lot of good vegetebles. Furthemore, Beef tongue is high in fat, which is one of those things you need especially in winter. Fat also gives that great tastes, and in the case of the Ox tongue, almost 75% of its calories are derived from this.
La langue de bœuf in french is literally translated as the Ox Tongue in English. However ox is an old and has very strong foundations and usage in the bible. There is even a old-fashioned, farming expression that pays tribute to the humble strong animal -- work like an ox. But this can also apply to all of us who slave in the kitchen :)
In more recent times however, especially in things pertaining to the kitchen or my plate, beef is usually the culinary term used. Except for the famous oxtail (queue de bœuf) - but I have no idea on why this is one of those exemptions.
Well, we hope that wets your appetite, don't forget to order on of the best la langue de bœuf by mail and otherwise, from no other than Les Délices d'Annie!
Bon appétit!
http://www.delicesdannie.com/