AbdulAlhazred
Legend
Players never think of everything. How do you know that they don't want to meet allies, as opposed to not thinking of something that they would have wanted to do had they thought of it?
While the example is cool and all, it appears that the player did not seek aid, but rather aid came as a result of his actions. Nor does it mean that the player will always remember aid as a possibility and mention it to you.
I think this is another example of being stuck in one way of thinking. The players in my game are FULL PARTNERS in the process of the RPG experience. This probably also goes for your earlier 'passive' comment. You see the players as some sort of lesser participants, almost like an audience, although I understand that isn't quite the right term. Still, like they only do this one limited thing in the game.
In my games the players DO think of everything. Because THEY ARE IN CHARGE of how they want to engage, they do think in terms of what should happen next. They know that if they evince a desire for allies, then a story about allies, the dangers, costs, and rewards of alliance, etc. would doubtless present itself, and it would almost have to take the form of some event or location intervening between the dwarves and the giant cave. It is PERFECTLY FEASIBLE for that to happen, and quite natural for the players to initiate it.
See, you, in your stream of consciousness sort of thing where every thinking moment of every character's life has to be portrayed regardless of its significance, and the players are wholly stuck in nothing but this mode, then what you say might be true, skipping something would be like 'fast forward' past some part of their lives, oh no! This isn't like that. We're arranging, in linear order, the pieces of a story of the players, playing game rules in order to decide some of it, and maybe doing other things to decide other parts.
Everyone is doing it, not exactly the same way, but its participatory, and thus the players minds are ranging over the story their characters are in and they're thinking about things like "Wait, my character always likes to hedge his bets, I'm sure he'd keep a sharp eye out for signs of anyone he could convince, or even pay, to come along and lend a hand..." This might translate into telling the GM "hey, Ted, we're traveling quite a ways to this cave, right? I'm going to use my Dungeoneering skill to look for signs of any folks I can talk to, or things I can use against the giants."