I have had exactly the same thought. My only guess is that the writers don't want to spend time on a bunch of speculative discussion by the characters that is not on track - instead they show us bits and pieces and let the audience do the speculating. Still when one character has information (such as Locke seeing the symbols on the counter), it would be nice to know how much, if anything, he has shared with the other characters.

Another frustration I have with the characters is how quickly the leave really interesting places without checking them out carefully. It I was there, I would have looked over every inch of that medical bunker, and would certainly have returned to the Black Rock by now. Sayid (and Locke, kind of) are about the only ones to do a decent amount of exploration. At least Michael was trying to figure out the computer in the Hatch, but I am off topic.