Yes, and sometimes, you will just heal a player despite having a proper substitute for him so that he can carry on playing matches and scoring and/or assisting (especially if he is the charts) just for your own satisfaction. Many users would want their players to the best, to break the records, to be always at the top in the charts and so on. It is just like when you support a real football team and would want the players that play for this team to excel everywhere including the charts and the awards.
There are players who will sell a player as if it is nothing though. This is the case mainly for users who do not have some sort of attachment, don't the sort of behaviour as described above or did not put much effort in getting the player or training the player. Others might also sell because they have no other option (no cover or the player who was supposed to act as cover was injured too, no money to buy tokens, no offers or not enough offers to get the required amount of tokens or packs); they have to sell else they risk losing matches that may be significant.