All players do, because it’s not actually possible. At best you can try and imagine how you might act if you lacked certain knowledge and act that way, but that is still acting on said knowledge, just differently than you would naturally do.
No, I understand why a DM might choose to hide that information from the players, what I’m asking is how the players could possibly not know the damage dice for a spell they can potentially learn? Like, I just know that Lightning Bolt does 8d6 damage because it’s a spell I’ve used before. As a player, I’m not going to stop knowing that just because the DM rolls those 8d6 behind their screen.