Sharp players may play differently against other players than they will against you
It is possible that sharp players will play differently against other players than they would against you. If you are a decent player yourself, the sharp players will likely know this and play against you accordingly. They may bet for value against weak calling stations, but would not when you are their opponent. They may call down aggressive semi-bluffers, but may not when you are the player doing the raising. They may semi-bluff the tight players, but may not if they think you are likely to call. It is useful to know what they think of you and how they will play against you in specific situations. All of this takes time in studying the players to pinpoint their level of understanding.