It doesn't require much space, it only needs to remember the bids for players currently on the TL. As soon as a player is bought the information is deleted (or compressed if BBs want to keep it). It allows us to check how many people are interested in a player, whether the owner of the player has been bidding on the player, whether a player selling for a lot of money got there reasonably by increasing bids or 1 person just came along and bid a lot and would indicate cheating.