Wow, interesting topic and observations. I have to agree that most backpackers I have seen are the youthful, adventurest types. I have seen OLDER backbackers too. I have come across a few backpackers in my days. I never really had the time nor job, to disappear for a few months at a time doing a backpacking tour anywhere. I saw the world working on board a vessel, which took me all over the world. BUT, what happens when we hit a port? We basically converted into "BACKPACKERS". That is where we carried our belongings, change of clothing, carried our souveniers or gifts back in our knapsacks or backpacks, or just plane travel toat bags. Don't forget, we have no cars to put our things in, nor do we live on shore. Our home is on the ship, and if we get stranded, its nice to have a toat with a set of clothing for the unexpected. I disappeared into the mountains in Northern Philippines with my backpack for 5 days when my ship harbored in MANILA BAY. Of course, I had more money than the average backpacker and could afford to stay in a 45 dollar a night hotel. Aside that, I was your basic backpacker. I was on foot, road the bus, and visited interesting sites around town. A backpacker to me is just a TOURIST with LESS money. Instead of using luggage, he carries a BACKPACK. He stays in cheaper places, but likes to linger in foreign countries for up to a month or more. Doesn't really have a career to go back to, and has alot of time on his hands.

I think some people tend to confuse a BACKPACKER with a CAMPER. A backpacker stays in economy HOSTLES and doesn't mind sharing communal bathrooms nor bedrooms. He doesn't know where he might stay from day to day, and everyday brings on a new and different enviroment. He tries to visit points of interest, to include climbing volcanos or walking through the jungles to see old ruins. If he's lucky and finds a decent HOSTEL for the night, he may linger in the lobby and utilize the internet over good coffee and as Europeans mostly do, converse about anything. If he has to, he may camp the night somewhere if he has no choice.
A CAMPER on the other hand, lives for the outdoors. He travels with SLEEPING outdoors in mind. A sleeping bag is a must, maybe a sleeping mat, a tent, he looks like he is carrying STEPS of equipment upon his back. He usually camps domestically, although, some do it abroad, but a CAMPER and a BACKPACKER are somewhat different breeds. One is in search of the outdoors fun while the other is in it for the "TOURISTY ADVENTURE".

Now, where does the Space Available or Non-rev fit into all of this? Again, they can convert to either a camper or backpacker when the plane lands, only, he did not have to pay FULL FARE, and if his wife works for the hotels and gets free lodging, this makes him the CHEAPEST SKATE with the highest traveling standards, and the ENVY of all in the travel world.