Jeff - ramblings more than an essay - if you want me to deep dive on any of this let me know. Otherwise use what you can.
In my opinion, based on my experience playing this great game, Traveller adventures follow the "Hero's Journey" template and typically follow the theme if not the plot of "The Magnificent Seven" - a motley group of strangers who choose or who are forced to work together to accomplish a mission or missions. Wanderers, nomad, "murder hobos" - Travellers themselves are restless, rootless people who don't fit into "society" as they perceive it. Some have tragic histories or criminal backgrounds, but all share the desire to "go boldly" rather than stay home and lead a "normal live." I have tried to imagine who our Travellers are in today's society. Certainly "the homeless" but they tend to stay nearby and have other issues that make them different from our Travellers. There was (perhaps still is) something called the Freight Train Riders Association - hobos riding the rails - and that template fits a bit but they again are not just on the margins of society they are marginalized by it. TV's "the A Team" is a bit closer to the Travellers we choose to play - veterans, skilled, moral/ethical people fighting for the little guy against the corrupt powerful. No member of royalty is going to troll a homeless shelter looking to pay people to solve their problems. If there are Travellers amongst us today they are loners who have learned to mask themselves as at least temporary team players. Look at shows like "Dangerous Catch" which is similar to a Traveller free trader in that the motley crew comes together for a mission and may stick together a bit but over time the names and faces change. When I play a Traveller I usually have to completely change my mindset of how I think I would be and act in similar situations - careful, cautious, quiet, suspicious, keeping my own counsel - because those things don't translate well into game play. Instead, I have to go into the game like a carefree innocent - shady patron? OK! Questionable legality? Sure! Sign me up. Putting other (usually strangers) ahead of my own safety and security? Why not - please, let me die so some other murder hobo might live and get rich by not having to split my share of the reward. Reality shows like "Survivor" or "Naked and Afraid" are live action role playing games, and those shows are rife with interpersonal drama and intrigue - usually amongst emotional immature people. No one wants to watch a group of happy go lucky people put their differences aside to achieve a common good. NO WAY - they want passive aggression, snide comments, conflict and backstabbing. NONE of that makes for good Traveller playing. So what we have is a disconnect of what real Travellers would do/be based on the psychology/sociology of people who would be compelled to be Travellers, and the filter which players have to refine/degrade those characteristics to "play the game" - literally, and well.
A true Traveller is likely an outsider, a loner. Perhaps they are high functioning well enough to spend a few terms or a career in the highly disciplined military. Essentially they are borderline criminals (vagrancy, questionable "work history") - think John Rambo traveling the country until he gets into that beef with the local cops. Certainly the gunfighters of the Magnificent Seven. I love the scene where Charles Bronson is introduced - he's chopping wood to earn his breakfast, and when asked about it by Yul Brenner he says "I'm doing this because I'm actually an eccentric millionaire."
Scouts are natural Travellers - hell, they are incentivized to do so. Merchants close to it, so long as they have a ship to crew with. Han Solo is a smuggler, not a Traveller - he has a ship, and he does illegal stuff. If you squint, Han and Luke go on a bit of a Traveller adventure when they sneak into the Death Star and bust out the Princess, but after that they "go legit" by joining the Rebellion. Harry (or is it Harvey) Mudd from Star Trek is a bit of a Traveller, as a con man. [This might be a good side bar - ask people whether classic Sci-Fi characters are Travellers, or show flashes of being Travellers].
Harry Flashman is a bit of a Traveller, as overtime he becomes more a mercenary rather than a career military officer. Firefly is frequently compared to Traveller and I see that but think they are evolved Travellers - they've found a "home." Shane the classic cowboy and the Man with No Name are Travellers.