At the end of Return of the Jedi, Luke is the most powerful person in the galaxy, because he is the strongest wielder of the Force. (Jedi mind tricks are the best argument against marrying him, come to think of it. “Those aren’t the chores you want me to do.”) He also has power as a commander in a military organization. He is so effective at his job (blowing stuff up, defeating baddies) that he is given the freedom to come and go as he pleases. He heads to Dagobah with a huge piece of Rebel Alliance property, and he waltzes in late for the meeting with Mon Mothma, but no one bats an eye.
Luke has an immense influence on those around him, because he brings out the qualities he needs in his comrades. This is a special kind of power. People do what he wants them to do, and he doesn’t have to force-choke them in order to persuade them. Han Solo is a scoundrel with a heart of gold, but it is Luke’s influence that turns him from a smuggler into a hero. He is the rising tide that lifts all boats no matter what the situation. He reminds Han Solo of his conscience, he inspires the other rebel pilots, he brings out the human in Darth Vader, and he even puts C3PO’s self-aggrandizement to good use. He uses people to the best of their abilities.
Although Luke begins the trilogy as a rube, he quickly develops better style.
This last outfit is the definition of cool. Simple black clothing is best when it is understated in a way that makes your sartorial choice look bolder than what everyone else is wearing. That is exactly what Luke achieves by wearing a minimalist ensemble while surrounded by the geared-up military uniforms of both the Empire and the Rebellion. His outfit says, quietly and firmly, “Weapons? I don’t need them.”
In sum, my first reaction to Luke Skywalker is that I’d like to be like him. I’d like to be frighteningly effective at my job and an integral part of a group of dynamic, interesting people that causes widespread change. I’d hope to be dressed well during this mission. So I’d be him, I’d marry him, or I’d fuck him, but I would never kill him, and I would never, ever undervalue him.