The idea of the Adventurer is a slightly silly one. That's not necessarily a bad thing - silly can be a lot of fun - but the idea of a bunch of heavily armed ass-kickers wandering around and leaping into life-threatening situations for fun is a bit odd. It's hard to fit that in the context of any kind of logical world. Most justifications (such as the idle rich, one of the few careers that lets you run around swinging a sword like a fool) end up flying in the face of other adventuring traditions (the idle rich don't need much loot, after all).
Because of this, most games (like most fiction) has at least some motive that necessitates the heroes take action. This is most often in the form of a threat which the heroes must face, but it can take other forms, like a quest. Curiously, the thinner the character is (say, an orphaned loner), the less work needs to go into this motive, because in a vacuum, all you need is a small push.
Players usually recognize the necessity of this motivation, and are often willing to put a little work at the outset establishing a pretense, and then just rolling with it from then on. The priority, after all,is to get onto the adventuring, and a thin veneer of justification is enough to speed that process.
Now, here's where you hit something that interests me. Most such heroes are reactive (or if they're proactive, it's in a very straight line). The threat rises, and they face it. If there's no threat, there's not a lot for them to do. Now, villains are proactive, and that's a good reason to play not-quite-heroes, but that solution doesn't always work. So I end up looking for another alternative for an easy way to construct a proactive hero.
Paradoxically, one of the best solutions I've thought of is the reluctant hero, a staple of fiction. This is the guy who, if he had a choice in the matter, wouldn't be adventuring, he'd be off doing something else; probably something normal.
Traditionally, this guy is a pain in the ass. A GM sees this sheet or hears this background, and red flags go up. If the character doesn't have a good reason to adventure, then odds are good that play will be unsatisfactory for everyone. If you have to spend your time fighting the player in order to get him to play, then something is deeply wrong.
This is one of the clearest possible examples of why the relationship between the GM and player is not truly an adversarial one. The GM is responsible for providing opposition, yes, but he does this as a partner to the player, not an enemy. If it were a truly adversarial relationship, it would end in mutually assured destruction as the GM drops infinite elephants on the character's head and the player decides he'd rather be doing something else.
But once the player realizes that this only works when he *wants* the GM to throw hard things at him, the dynamic shifts drastically, and a lot of things that had been roadblocks can make the game better.
Taking the specific example of reluctance - from a player who understands that what he really wants to do is play, not find excuses not to play, reluctance is an invitation. It says to the GM "Let's make sure my reasons to engage have some teeth. I'm not looking for an excuse to adventure, I'm looking for a reason". Now, this is absolutely a challenge, demanding that the GM step up as well, but GMs need that to keep themselves from getting flabby.
So if you can end up with a character like this, consider what you now have: a strongly motivated, well fleshed out character with reason's to act beyond the immediate plot. Whatever is motivating the character to act is an obvious character hook for other events and conflicts. You have a character who has an understanding of what he wants, understands why he's doing what he's doing, and who will - if left alone - step up and start getting proactive in pursuit of his larger goal. All without needing to be a lovable rogue or dashing scoundrel.
Anyway, this isn't a step I would suggest for every game or for every player, but next time you sit down to do character creation, consider arguing for why a character shouldn't be adventuring. Putting the player is the position of arguing his case helps him think about it in ways he might not have, and gets him more invested in the arguments he puts forward. This could be as informal as a conversation or as formal as a phase in FATE committed to "Reasons to Stay Home" but simply having the conversation can tell you a lot about the player, and can really lay a solid foundation for your game.
1 - Not that a logical world is a necessity.
2 - The player also, implicitly, needs to step up. it's a partnership.
3 - And, seriously, I love me some Han Solo action, but other archetypes deserve the chance to be cool.