But I Still Give 'em One!
With true, rules-light OSR systems, PC's really don't often last long enough to have a background be meaningful. No matter how skillfully or carefully one plays them, the chance of dying is very high in the game where 'save or die' is the modus operandi. That's fine with me, as I came up in that world. I was born and forged in the fires of a game that tried to kill any and all who sought fortune and fame within its bounds. I don't care though, because I still give my guys a short background. In this case, it gives me something to say about them as they are buried in the folder with their adventuring brethren. Even level 1's deserve a few, short words spoken over them as they greet the great beyond.
I've had the opportunity to play in a few 5e games now, which means I've created a few characters in that ruleset. In the past, creating my characters has been one of my favorite parts of the game. With OSR rulesets, character creation is a fairly quick process once it's been done a couple of times, even by a new player. I like the process regardless of how the DM house-rules it, so play the numbers where they lie, or mix it up...whichever. I usually end up with a PC I can get behind and enjoy playing. Even when the DM hasn't called for it, and the chances are high that the PC won't even last a full session, I tend to write a few sentences about that characters life, his history, his past...in other words, a background.
In 5e, the background bit is built in to the ruleset, so as you create your character you pick up/roll for traits, flaws, bonds etc. I understand why they baked it in, but I don't like it one bit. New DM's are likely (as I and many folks were) to follow the rules/guidelines as written. They don't have to of course, they can choose to ignore this part of character creation entirely, or mold the process into anything they choose it to be. Instead I have the sneaky suspicion that players fill these fields out, and give little further thought to them, or if they do, only in passing. In a game where survival is high, I think that players should be encouraged to really flesh out a background, perhaps even writing a page or two. After all, 5e has death saves, short rests, and a host of other ways to keep the PC's alive and kicking so there's no harm in a bit of background investment.
As a player, I create a background for each PC regardless of the DMs rules. I find that my character isn't complete without me knowing something about him. It's not always the same things, sometimes I work out some family history, other times a terrible incident that led him to become an adventurer, and at times I just list a few traits and flaws so I have a key to his behavior. It all depends on the character class and stats, the game I'm going to play, and most of all my mood.
When I'm in the DM's chair, I often rely on the players to offer up some sort of character background. I live between the sandbox and the railroad, and my game world grows very organically through play. The backgrounds of the characters help to forge the foundation for much of the game-space. This is less of an issue when I run Holmes or Labyrinth Lord (without the AEC) or Swords & Wizardry, but as I creep into more advanced rulesets like 1e and Castles & Crusades (or add the AEC to my LL game) I find that story and history of the game world take more of my time and energy and the backgrounds become a focal point for some or all of the characters.
As an example, a player who's character is born in poverty, a bastard child who grows to become a dangerous fighter, may have a father of unusual racial descent. Another player may come from great wealth and/or nobility, and being a third son is sent away to study with a mage of questionable morals and ethics. You can see that a little goes a long way.
I know that for new players, writing a background (however brief) may not be something they know how to do or understand. Here is where the DM should step in. Do a bit of hand-holding and talk the player through the process. "Did you have parents? What did they do to earn money? Did you grow up rich or poor? How did you get that sword you now have?" are all great questions to both help the player determine an background, as well as get that players juices flowing for more information about the character, information yet to be played out!
Some DM's play sans backgrounds of any kind. For many people, playing the game as-is and having the players amass only new history without having any origin story or similar background information getting in the way of the 'here and now' of it all is as valid as any other mode. I find this not as enjoyable, but that doesn't mean it's wrong. Regardless of how much time and effort I put into any character, I realize they can end up as food for a hungry Owlbear or on the wrong end of a goblins rusty blade. A game where death is not omnipresent is problematic for me, but that's another post altogether.