In TX, it's illegal to sell any part of a wild animal not specifically designated a "Fur-Bearing Animal." One must also possess a Trapper's license to hunt these animals and trade in them, except for Bobcat, for which one may possess up to 2 w/out a trapper's license, if memory serves...
The whole concept, I suppose, is to keep people from making a major market out of game animals like deer, and setting it up such that it would be profitable to trade in their meat or hides, and thus profitable to poach 'em. At the gun shows, when you get samples of venison jerky from the jerky manufacturers, they can't sell you a pound of deer jerky, because they'd be breaking the law. Instead, they'll sell you a pound of beef jerky then, and give you a card to call them to process the meat after you kill out.
This seems to be a spill-over from the halting of market-hunting for water-fowl that went on back in the early part of this century past, which nearly rendered the extinction of some species of ducks and geese. Overreaction dies hard. (Those market hunters had few, if any, restrictions on the actual numbers of birds that they could take.)