LionsLair: That actually came up a long time ago when Fencer was first introducing the game. Since the cube has been added to all the gammon games (6 versions currently), Fencer did not really want to add a variant for the cube version and double the number of games. (Then the question of doing it like other sites and make 3 points cube version a different game then a 5 point cube version, etc...)

In the end, Fencer liked the idea of making the cube an additional "option" to the game rather then making it a new game.