New gamers find the worlds they explore full of stories. Some are wonderful. Some aren't. But there's so much to read and enjoy that it all averages out to a good time.
However, the older gamers have a more intimate relationship with the fluff. The problem with this is that these stories keep getting added to, and the new authors have their own ideas, some of which don't mesh with the older established canon.
I ran into this in Warhammer 40K around the time the 4th edition Space Marine codex came out. Some authors were writing about what no man should write about: The Horus Heresy. In this fluff, the Salamanders Space Marine Chapter was changed. They used to be the "space black people." While this was pretty racist, at least there WERE some black people in 40K. Everyone else seemed like they were direct descendants of europeans.
The Horus Heresy novels and the 4th edition Space Marine codex changed that. Now they weren't african black, they were BLACK black. Like Chaos black. Like the darkest night that crushes your dreams. Plus they had glowing red eyes. Not only did this invalidate all the fluff previously written by GW or by fans, it also made people's paint jobs not reflect the background anymore. Plus black skin and red eyes looks stupid.
My Space Marine chapter, the Azure Flames, was a Vulkan successor. So, I retconned my OWN fluff and altered the background so that they were mysteriously not jet black with red eyes.
The Azure Flames have the distinction of being the first official successor chapter to inherit Vulkan's Gene-Seed. This has led to some uncomfortable questions. It is rumored that the Salamanders have jet black skin and glowing red eyes. It is quite obvious that this is not the case with the Azure Flames, as they exhibit a remarkable range of skin, hair, and eye colors. Perhaps the Azure Flames have a mutated Gene Seed which reacts to radiation differently, or perhaps the seeds for the appropriate organelles were taken from a different Primarch. Whatever the reason, the Techpriests of Mars and the Apothecaries of the Azure Flames do not speak of it.
This is not limited to GW. Privateer Press retconned several facts about the Cygnar character Allister Caine. Sadly, no matter what you think, canon is canon. You can't make GW NOT have changed the official fluff. So you either adapt to it, or you become a cranky old man who wakes up screaming at night that Ork blood is green.