Immersion comes up a lot when discussing RPGs, typically in response to this style of game making it more difficult or easier for one person or the other to experience it.
The thing is, RPGs are a really poor choice for an immersive experience. I know that we've been told that this is something that's at least a byproduct of role playing, and it's desirable, and for a lot of people is a goal. And it's not a bad goal, either, and it's no reason that if your intent is immersion to not at least try. But at the very least, one has to recognize the odds are stacked against someone who wants to minimize breaking immersion.
Now, before people get out their pitchforks and torches, give me a chance to explain. Most immersive experiences that non-gamers are familiar with - say a movie or a book or a video game - are relatively solitary and internalized affairs. You get so wrapped up in the experience that you feel you're really there and forget about being yourself for a little bit. Sure, there might be things that bump you out of it - phone rings, the kids get too loud, the computer/console crashes - but overall the number of things that you have to interact with to sustain immersion are minimized.
Also, this is not a diatribe against immersion, nor in any way meant to invalidate, belittle, or otherwise tell people for whom its important that it's a pipe dream, doesn't exist, or anything else. It's just a short examination as to why rpgs actually wind up not being the perfect environment for it - in spite of most common thought that immersion is a natural outgrowth of playing rpgs. You have to work at it, in large part because of the activity's format. In some ways, perhaps more, this may be more commentary on why you can't get away from metagaming.
First, we have the game part. You need to interface with the rules in order to play the game. Granted,when game systems "fade into the background" - often as much through familiarity as elegant design - it makes immersion easier. Some people can get immersed even when the system is front and center. But rules and game systems are still artificial, and require bringing an internal process (the immersion) out into an artificial framework. While mechanics can certainly help in certain ways, they can cause a disconnect much more often. I still strongly believe that you actually can't design a system to support immersion - you can accomplish any number of other goals that might help support it, but it's a corollary instead of the primary result. Compare this with, for example, a PC game. While you still have to wrangle with controls, they tend to get out of the way a lot faster than rpg mechanics do - and they're easier to manipulate if you have the money and inclination to go with nonstandard control schemes that can be reconfigured to support playing the game better (i.e., any number of input devices from Razer).
Next, you have the inherently social activity of RPGs. I think that this has a bigger impact on creating a flawed environment for immersion than the rules do. In order to interact with a group of people, you again have to externalize a purely internal process. So now we have two external filters - the rules and the expression of character - to deal with. Again, the social group can do a lot to build up immersion but there are just as many ways (if not more) that someone can do something that pulls you out of "the zone" (for whatever measure of "the zone" that there is for you).
Finally, we have the environment. You can turn down the lights and sit down with headphones for a movie or a video game or a book. You can get yourself in a comfortable and quiet place. Not so with a group activity like an rpg. I mean, everyone could be in really comfy spots in a space with lots of atmosphere to play an rpg (and this is totally a good idea), but the environment is still a shared one and not a private one. That's another ding against an rpg being an ideal place to bring the immersion.
Does that mean that immersion doesn't exist or isn't important? Nope on both counts. But those things that are working against it don't necessarily affect other elements of play. You can enjoy all of the other elements as they are even if the mechanics are wonky or the players or environment are distracting. The traditional structure and mode of playing RPGs simply wasn't designed with immersion in mind and this goes a long way toward explaining explains why it can be so difficult.