Give Them Details (part 2), Gratuitous Details
Details are good, and can make the game feel more real to the players. But there's a flip side, which is that gratuitous details can alienate your players.
It's about suspension of disbelief: if the players perceive the details as a natural part of the game world, the details will improve their game experience. If they suspect that the details are only there to make the world feel more real, it will backlash. The players will spot the GM's hand and recognize that they are being manipulated by the game world rather than just living in it.
Real world details are less likely to backlash than made-up details. You can talk about a character's involvement in the WWII Africa campaign all day long, and even if it's boring the players will not see it as artifice. But if you go on dropping lists of fictional historical battles, the lieutenants involved, the colors of the banners, and so on, players are more likely to stop buying into it, because they _know_ you made it all up just for them. Of course it's not like you get to choose: if you are running a game about WWII you have real details, but there's no such thing as real details of the Ursa-Elf Conflagration of the Late 7th Millennium. The point is to recognize that the “safe” amount of detail is not the same in all cases.
The greater resistance to made-up details might also be part of people's natural resistance to buying into and submitting to another person's creativity, but that's an entirely separate discussion.
From this discussion you might think I'm saying that all details are just there to impress the players, but of course this isn't the case. Most details are there because the GM sees them in the game world whether he intends to or not. They are things the GM believes are “real” facts within the game world, not a facade constructed to entertain the players. Even if no one was listening, the GM would still wonder what kind of cloaks they wear in Scolfane.