As I've often said, I enjoy a certain amount of "reality" in my game. That is, there cannot be smoke without fire. Sorry, but it just doesn't work. An example of this is a mixing of the Game's races.
An illustration I like to use comes from the movie "The Quiet Man," starring John Wayne, Maureen O'Hara, Ward Bond, Victor Mclaglen et al. Yes, I know some of you will have to Google that movie and those names, no problem; you will not be the first to accuse me of being "older than dirt." LOL
Anyway, in the movie, John Wayne is in the Pub and offers to buy everyone a drink. No one, but no one, "rushes" to the bar for the free drink, it is only after it is established that John Wayne is the son of 'so-and-so' and the grandson of 'so-and-so' that an older man says: "Well now, that being the case . . . we will have that drink!"
I will point out here that, not only is everyone in the Pub is white, they are all Irish! Yet, in spite of that fact, no one was in a hurry to drink with a "stranger." We see this happen in real life even more when the stranger is of another skin color. So why is it that, in the game, everyone just assumes that Elves, Dwarves and Men rush to adventure with each other?
In the City of Greyhawk, each of the races has their section of town in which they "hang out." While it might not be "Rare" to see a human drinking in a Dwarven establishment, it is certainly "Uncommon" . . . or it should be. The same applies to an Elven establishment. While the human might be in there drinking, there wouldn't be any Dwarves or Elves patting him on the back and regaling him with their tales. He's both a stranger and of another race.
I'm not saying the races are enemies, nor that the demi-humans hate the human drinking in their midst. I'm just saying that no one is acting as though the human were a long, lost "buddy." They're going to act a little "standoffish" towards him; accepting his presence, rather than accepting him.
We won't even discuss the fact that both Dwarves and Elves hate Orcs, complicating matters when adding a Half-orc to the group.
Baring this in mind, I like my players to have back-stories explaining their presence in the group. Why is a Dwarf adventuring with an Elf and how did they "end up" with the human? This gives the game a more realistic feel.
Exclamation: "Oh Mystic! It's just fantasy!"
Reply: "You know you really need to be gaming with someone else."
I prefer something like this: The human and the Elf know each other from "back when" and are now adventuring together. They come across a group of Orcs that apparently have "someone" holed up in a crevice, or copse. The human and Elf effect a "rescue" and . . . behold! . . . it's a Dwarf! Now the three of them adventure together!
I actually enjoy running that type of scenario as well, as a way of adding a character to the game. Of course, the game can start out with the various races adventuring together, I just appreciate my players getting together and creating a back-story that explains how they all ended up together.
Sadly, I find that I usually have to create the back-story . . . I game with some very lazy players. The detail that they put into their own characters often leaves something lacking as well. They want the "hack and slash," not the role playing. Alas, they are all I have for gaming partners and so I am forced to "make do."
Regrettably, it can make for some uninteresting gaming. I do have one player that will put forth the effort, though I do need to "nudge" him to it. If it weren't for him, I'd stick to my computer games and let the others "suffer." Without me, they don't have enough people to make a game. Even then, I need to run two PCs! LOL
Anyway, that's another area in which I like a certain amount of reality in my game. What about you? Do you care about it at all, or are you happy -- as a DM or Player – to just "hack and slash?"
Let me know. I can foresee several discussions on this particular point.