>For fantasy stuff, people mean D&D. It is very easy to work out from context if it is Eberron, FR, etc.
Do they, though?
Or do they mean one of the billions of other fantasy roleplaying games out there, or generic animu trash (hello, "elf stuck in tree" threads), or just a generic "setting" that encompasses all of media?
Hell, if someone talks about Orks specifically that's either 40k or Warhammer Fantasy - but that's because they spelt it with a K. If they said "Orc", did they mean the noble savages of D&D, the pig-faced orcs of old D&D, the Orcs of middle-earth, or animu bullshit?
Hell, what about kobolds? Are they furry or scaly? Do they have any relation to dragons whatsoever? Are they cutebolds, or are they germanic spirits, or what?
Even when something is "D&D", there's a lot of difference there! TSR D&D is a very different beast from WotC D&D, and even within WotC's "default" setting you've got at least three separate cosmologies!
And that's without getting into the non-published settings that individual DMs create for their games, where "God" might mean more than just a ton of hit points and free spells.
Oftentimes, "depends on the setting" is a very relevant question since there's a hell of a lot that actually depends on the setting! Even dumb questions like "why don't Wizards rule the world?" have a ton of assumptions you need to work through before being able to answer it properly.
For some of those threads, it's all just down to memes. Why do elves hate dwarves? 'Cause Tolkien did it and people copy him. They don't in individual settings, though, and thinking about it I'm not even sure that there's a current D&D setting where that's the case?
But it's still a meme, so it sticks around. Dwarves hate elves and are scottish, elves are slutty hippies, humans live in feudal kingdoms, guns aren't a thing despite 17th century armor, magic is rare and special and can do anything.