It is highly useful in seven-card stud to be able to recall the cards that have been folded. This is true for two reasons chiefly.
By knowing the cards that have been folded, the astute and thoughtful player will be better able to know the likelihood of the as-of-yet unseen cards that remain to be dealt. Secondly, by combining the cards the player has seen with a knowledge of the cards that have been folded, along with the betting of the other players, that player will better be able to assess the cards that are held by his opponents.