We already know Luke wants to fight the Empire. He said as much while still on Tatooine. But notice what he does when he first encounters the Death Star. He could take that Empire on in a head to head fight... and get stomped. Instead, he ends up (along with Obi Wan, Han, and Chewie) setting more achievable goals - rescue the princess and escape. What's to stop a group of players from doing the same thing? Set their own goals based on a situation that, if they take it head on, they currently cannot solve or defeat.
And we see this a number of times in the inspirational literature. Malcolm Reynolds may know he can't get through an Alliance fleet to get to Mr. Universe so he engages in an activity within his reach - goading a Reaver fleet into pursuing him. Gandalf knows he can't take the One Ring and swoop into Mordor with it - that's way too conspicuous. But he does have the power to get some of the most innocent, stalwart, and stealthy guys on the planet to sneak the ring to the Fire while he and his buddies keep the Eye focused on other events.
You may see things as if a GM had set up these specific challenges for the PCs - ones within their grasp. But it's just as easy to see it from a more sandboxy perspective with overall goals (destroying the Empire, getting to Mr. Universe) and let the PCs choose what they do to achieve them, how, and when.