Complete lack of balls on the part of bookmakers and inability to garner even activity on these props.
When they do dare offer them - they will juice them ridiculously.
Too many copy cats and not enough people researching and setting a line and even less shops who have the willingness to assume risk. If a book wants to attract pro level play - they offer things like this.
By not offering these bets - you can gauge the interest of most books in handling pro level action.