http://www.nytimes.com/2011/08/03/dining/reviews/boxed-wines-review.html?pagewanted=all
There are two reasons you don't get expensive or high quality wine in bag in boxes. THe first one is purely image. We, as people, are highly swayed by the outer packaging. Wine is somehow supposed to be classy, upscale and somehow, a box doesn't fit our sensibilities. Because of this, people (in general) prefer glass vessels (usually with corks) over screw caps, bag in box, or kegs.
This does mean that shipping, and cost of the vessel makes a wine more expensive, but cost is part of image as well. We think of an expensive drink to be better. (Often this is the case, but sometimes price has less to do with quality, and is due to cost, or attempting to raise the perception of the item/wine itself).
Haven't we all seen where we have made a decent drink, wine, mead, beer, but the bottles wind up costing the same amount or even more than the drink inside?
The second is material. Because there hasn't been as high a demand, there would be less people willing to use it, and less people willing to research to improve the barrier material. Back when, there wasn't money involved. It was better to make a funky looking bottle of glass and charge extra then to research plastic material for a box, since boxes had the perception of low quality. If this is the case, why put a quality wine in it?
There's some redesign in thinking in the past few years. Packaging waste, packaging cost due to weight and space requirements, so it's quite possible that bag in boxes will wind up being improved.
That said, I still don't think I'd age a wine in a bag in box, or put some really expensive wine in it. (Actually, I'd age the wine in a stainless steel vessel, a keg). But I'd really love to have a spare bag in box or two filled with anywhere from cheap, to at least decent wine, to be easily used for traveling.
