As time passes, more and more Tribble Species are "discovered", and less and less space is available for the Captains that adopt these loveable little fuzzballs.
Right now, Memory Alpha Crafting effectively takes up around 1/3rd of a Player's Bank space and 1/4 of a ship's free cargo space. Then there are the tribbles, all 32 species of them. It all tends to make a player's space rather.........crowded.
32? i could have sworn there was only 31? (including the holo tribble)