Some of this certainly makes sense. If you or your character aren't a complete stranger in a given area, there's no reason why they should be completely without acquaintances. Now, if they've just moved to a new area, joined a new squad, signed on aboard a new starship, or what have you, in those cases it does make sense that you're -just- beginning to make a name for yourself and become a part of the community/crew/squad/etc. However, if that's not the case, it's tough being introduced to a new setting when the character you play shouldn't need introductions.
That, I think, is why in some cases you get this anomaly in games. The character may not need re-introducing to the world, but the player does. In order to do this, you have to either help the player get established within gameplay -or- you need to provide exposition of some kind; cut scenes, readable books/computers/something in the game for people to peruse to get the back story, hell even some flavor text in the game manual can help. The problem is some gamers have a real problem with this sort of exposition (in particular the cut scenes) and bash it as not immersing a player into the world. Personally, I like in medias rez, but you can't have your cake and eat it too. And some games just have a need for cutscenes; frankly I like them when they're well done and fun to watch. I just wouldn't rely on them too much or make them needless.
Making a player character a part of the world they exist in (or failing to do so) can make or break a game. But HOW a character's place in the world is established needs to be handled properly, or it will feel awkward and mar the overall experience.
Loved this piece, it fully revealed the reason I liked AC2 over AC, AC:B, AC:R and Far Cry 3.