It seems like you are saying "no backstory" = "can't do anything but orc and pie".
I don't know why it would seem like that. I'm only offering up orc and pie as an example of a sort of gameplay where backstory wouldn't be required - though of course, you could play orc and pie with backstories if you wanted. I'm sure that there are a great many more examples, but I was trying to explain why I felt backstory was a required thing. That's why it was necessary to go through a lengthy list of things to explain why I found it necessary to have a backstory in a game which normally is not assumed to and doesn't require it. Otherwise people might say to me, "What's this? Behold, I play without backstory! Away with your thrice-cursed foolery, for never a game of D&D existed that it required a back story!"
I think that shows a narrow vision of the possible.
Irony. I have narrow vision, but you are the one that goes from my "Not only..." to "Either backstory or orc and pie."
What I'm talking about isn't really specific to D&D. I'm running Deadlands and Shadowrun campaigns - both classless systems.
I didn't say it was specific to D&D, but since I was talking of a D&D game my contrary examples were drawn from D&D. Again, strong 'class = role = character' would conceivably mean back stories are not required. Alternatively, very high granularity in character creation would allow you to establish a characters identity through point buy advantages, disadvantages, quirks, etc. GURPS largely fills out an identity via point buy. Burning Wheel is practically character generation through backstory creation.
The NPCs react to however the characters present themselves at the time. How are they dressed? How do they behave? That determines reaction.
Sure. And you could add to that accent, vocabulary, hair color, skin tone, instinctive gestures, and a variety of other signifiers. A character could of course disguise themselves as something that they are not, but it wouldn't take Sherlock Holmes to deduce a very large number of things about a character just at a glance and after a few words. An Innkeeper would be very good at it as a point of his trade - it pays to know who you are letting rooms to.
In a modern world, with a widespread monoculture cultivated by ideas about democracy and individualism, spread through mass media, enforced by near universal education, and enabled by consumerism and mass production, it certainly could be the case that he is 'Just a guy' and no one really cares. He swipes his credit card through the slot and a machine validates it - what more is needed? Nothing says social alienation like the 20th or 21st century. But in a society of limited mobility and many social and legal castes of persons, being 'just a guy' requires considerable skill at disguise and is likely to unnerve people. Anyone who presents a conundrum, who can't be easily labeled, provokes both fear and curiosity. There are of course inns and taverns where they know better than to ask questions, but staying in that sort of place has its own problems.
Think about the hobbits staying at the Inn in Bree and trying to be 'just some guys'. Well, first, no Shire hobbit is going to be able to disguise where they are from, and the Breelanders are almost certainly going to be able to recognize a Bucklander by his tongue - and a member of the House of Brandybuck by the better cut of his clothes. So Merry is almost a dead give away to anyone with eyes. Additionally, no respectable inn is going to let a room without a name, so Frodo has to say he's Mr. Underhill - sort of the equivalent of saying he's Mr. Smith. But that doesn't work to well either, because there are some Mr. Underhills in the room and they'd like to know who he's related to. Now, because hobbits are mad about genealogy, this presents Frodo with a huge problem. If he feigns disinterest, he's automatically suspicious and clearly trying to hide his identity. Otherwise he has to spin an elaborate family backstory for himself on the spot, and yet somehow manage to make it ring true and not end up claiming to know someone someone in the room does. Meanwhile, there are also curious questions as to what brings hobbits from the Shire out to Bree. The presence of at least one member of the hobbit aristocracy provides a ready answer - these are adventures in the old sense of tourists, out on a lark. But that connection makes it rather harder to hide their family connections to the Baggins, which becomes a problem rather quickly when Pippin begins telling stories about Old Bilbo - a problem exacerbated by the fact that Mr. Frodo's leaving Bag End was impossible to keep out of the rumor mill. Pretty soon even some of the slower hobbits in the room are taking what they know of Brandybuck and Took genealogy and figuring out who the mysterious Mr. Underhill might be.
And of course, all this blows up in their face, because eventually they get taken for warlocks of an evil disposition once Frodo does something uncanny under pressure to maintain his disguise. The same sort of thing would happen to characters in my game if they can't hang an easy sign on themselves that lets them be pigeon holed into someone's stereotype. If you aren't clearly a member of society, then you are antisocial in the old sense, and perhaps inhuman.
Think about Kim with its world of identities written in peoples clothes and manners.
And even today, people can play this sort of game if they care to. I walked by one kid at the mall playing the game, "Guess the occupation." with his friends. He guessed for me, "Engineer." That's fairly close, and its far harder to play that game now than in the middle ages or in India of the not to distant past.
The point being is I play in a world filled up by pouring Tolkien, Kipling, Lovecraft, and the like into it. That's what I play. I don't know what you play. I can only tell you what I play.
One of the running gags in my current campaign is one of the characters asked for an obscure past, and everyone is always recognizing things about him he doesn't know himself, and assuming he knows of things he in fact doesn't.
It's been 20 years since I played much without a back story being assumed to be something you did, regardless of system. It might only be a few broad strokes in seven sentences or less, or it might be a 5 page essay depending on the game to be played, but it was there.
