The justification for the use of capsules, at least as far as we see it, is twofold:
1. Completing a visual or aesthetic as part of the package.
2. A tamper-evident barrier.
When we were playing around with putting together a new look for the Ice Wine, I was an advocate for the "minimalist" no-capsule or wax look. I think it looks really cool, and has been used to great effect by Owen Roe and others. Capsules are expensive as well: a custom tin capsule can be upwards of $0.30 each. We make ~35,000 cases of wine per year, so the use of capsules makes a significant difference on our end of year profit loss statement ($0.30 x 12 per case x 35,000 = $129,600 per year.... yikes!). Even when we use a cheaper polylam material instead of tin, (around $0.05 to $0.10 each) the cost is not insignificant.
That's right. There are two kinds of metal capsules we use, and each has its pros and cons. The tin capsules generally have a more premium look. They take ink better, are more malleable (meaning they wrap around the neck of the bottle better, reducing the likelihood of wrinkling), and do not have a seam down one side. Polylam capsules are much cheaper, but generally aren't as good all around aesthetically and in application/logistics of bottling.
Any guess as to which bottle (below) is a tin and which is a polylam?
The answer, and work with me here, is that the cork is perhaps the only enclosure in the entire packaged food/beverage industry that is not tamper-evident. Try to open a Coke bottle (lose the seal), a can of beer, a screwcap, a bag of Doritos, a Lunchable, or anything else that you could buy at the grocery store with a barcode on it and make it look like it wasn't messed with. Hard to do. Especially with a two-prong, it's fairly easy to take out a cork with no physical/visual evidence. A capsule is simply a barrier that makes it that much harder, especially on a larger scale, to mess with what's inside a bottle of wine. Wax accomplishes the same goal (and especially in Native Sun's case, looks fantastic in my opinion) but there is also some consumer backlash from an ease-of-use point of view there.
So it protects us from unsavory business, and it protects the consumer with the "promise" from the producer that what's inside the bottle is what we want to be in the bottle. It's kind of like putting a bow on it.
Paranoid? Probably. But stranger things have happened.