[Skarg]

TFT does have several places where it states and/or suggests when rolls should be hidden or even rolled by whoever the opponent is. For example, when disbelieving illusions.

SJ understood the need for this especially when playing TFT as a two-player game as opponents with no referee, and he also made several suggestions in ITL where it makes sense not to share rolls with the players or even say what the GM is rolling for. For example, when rolling to see if the PC's notice something that, if they fail, they should not even know there was something to notice but their PCs failed to notice it.

I understand that many players like to roll dice and see dice rolls, and sometimes it's interesting and appropriate enough as a way for players to learn what's going on by observing the rolls and results, but my players and I fairly quickly appreciated that there is a different kind of value in not seeing the rolls, and having the GM instead give clues when appropriate. For example, the difference between getting hit with a weapon, seeing the roll, and being able to tell if it does more damage than normal because you saw the roll and get told how much damage you took: ("GM rolled a 5 but I took 8 damage - it must do +3 damage and be magical!"), versus being hinted or told (or not) by the GM that the weapon seemed to strike much harder than expected, but still needing to cast Analyze Magic to know exactly how powerful it is.

Not all players prefer the same things - some enjoy the experience of having to figure things out in character.