I tend to ramble a lot; this next part in quote-format is simply back-story to why I've posted about this issue. I would advise skipping the next part and getting to the real question, unless of course you're interested in my back-story--in which case, I greatly appreciate said interest! 
All my dithering aside, what are some effective methods that a DM can employ in order to promote immersion--to tell the players that spending hours making detailed back-stories, belting out archaic speech in hammy voices, viewing the NPCs as real people rather than figments of our group's collective imagination, and taking the time to learn the inconsequential details about the world they roam is in fact a worthwhile task?
Thanks for reading! I apologize for the wall of text, but... well, I tend to really get way too deep into things, as you may have inferred by now.

I'm part of a group where the DM's role is passed around a lot; this lets all the players have a chance to experience the game behind and in front of the screen, keeps the ideas fresh between adventures, and makes sure that the DM isn't "burned out" by the increased workload involved in running a game (we're all students, so time is quite short, especially heading towards the end of the school year.)
However, this method has a number of inherent issues; we had to incorporate a "dungeon-of-the-week" episodic campaign in order to tie the often wildly disparate adventures together, meaning continuity is often ruined as the DM role is shifted around.
This is the heart of what is seeming to happen with my game group.
Since there is very little continuity between the sessions, it seems that some of the gamers in my group are "losing focus" and starting to lose immersion in the world, the nation-shattering wars and problems within it--and unfortunately, even with their own characters and the adventures themselves. It's becoming increasingly hard for the current DM to keep the group on track, which is unfortunate because I enjoy the story he's spinning for us.
It will soon be my turn to run the group. I quite enjoy participating in and making stories with detailed characterization and a plot where the stakes are often just as personal and emotionally-driven as they are epic (I've even had to handle romances between the characters in a different party); however, I'm viewing the current situation and it's becoming obvious that such an approach could fall short if the gamers aren't willing to take the world seriously.
I am quite prepared to change the focus of my adventure completely if it doesn't seem to be working at all with the game group, but I think good role-playing is integral to an RPG ("RPG" does stand for "role-playing game," after all), and would rather try to bring back good-old RP'ing rather than simply go along with the "gaming" aspect of RPG's--or worse, scrap the setting if gamers lose interest entirely.
All my dithering aside, what are some effective methods that a DM can employ in order to promote immersion--to tell the players that spending hours making detailed back-stories, belting out archaic speech in hammy voices, viewing the NPCs as real people rather than figments of our group's collective imagination, and taking the time to learn the inconsequential details about the world they roam is in fact a worthwhile task?
Thanks for reading! I apologize for the wall of text, but... well, I tend to really get way too deep into things, as you may have inferred by now.
