I began to observe "Nerf Culture" during the very beginning of League of Legends. Prior to that, you had games that either never changed (early fighters), rarely changed (re-released games, like Melee), required an entirely new game to change (Street Fighter), or never experienced nerfs (Runescape, early MMOs).
When games like League were introduced, it generated something unique: shallow number of options that can be used in deep ways. 4 abilities and a passive unique to the character, plus 2 additional abilities available to everyone. This allowed for 2 things: Balance changes could be easily implemented and the game was very easy to pick up, learn, and play. But this had a very specific issue: Riot Games' policy was almost always to nerf and not buff, or to rework. Buffs came from time to time, but nerfs were more common.
This made way for the foundation of, "Nerf Culture:" If the playerbase demanded a nerf, they might just get it. Doing this is far, far easier then dealing with the thing that they are asking to be nerfed. Therefore, if they ask for a nerf, the whole situation would be handled and they won't have to do any of the work that would of otherwise been required to beat that thing. They did not need to "git gud." Devs took care of their issue for them.
Ever since that instance, I've noticed it come up in a ton of other things, such as DotA, HON, Overwatch, Street Fighter, etc. Anything you can go against someone to prove you're "better" and win. I'm not saying LoL created this, but it's when I first noticed it and is the prime example.
But then, here's the issue: too many buffs and nerfs can kill a game. Each change requires players to adapt to said change. In low option, high depth games, like League and DotA, this isn't a big issue. How you use your options is the bigger deal, even if they don't have as much reward post-nerf, or can't be used as often. In high option, high depth games, such as fighters, Hearthstone, etc., a change to an option can have a much, much more severe impact. There are options that are simply not used because reward/risk ratios are so skewed. A change to a fundamental option can change how entire characters are played and fought against.
Because of this, early, kneejerk nerfs to characters can irreparably damage a character because we're still figuring out every character's options and how to use said options. I'll use Little Mac as an example. He destroyed new players because he had unique aspects of his options that people could grasp really quickly, but couldn't quickly figure out how to beat. So, he was hit very early on. As it turns out, he's one of the worst characters in the game. He likely still would be even if he was never touched, but it took time to figure him out. It took time to find the counterplay. He ended up way, way worse off because the devs responded to "Nerf Culture" and hit Mac's weakness hard, turning him into a joke. It was never needed, it was never really warranted, but the "Nerf Culture" took hold.
So that's the issue with asking for nerfs early on: The game is undeveloped. It takes months to fully explore a character, figure out that character's matchups, and really dig deep to find the strengths, options, and style of a given character. If you hit a character that ultimately doesn't need it, it does damage that might not even be needed.
It's easier to ask for a nerf then to figure those things out for yourself. That is nerf culture.