The reason wine goes bad is because oxygen wants to turn wine to vinegar, and it happens at an alarming speed (as fast as 48 hours). When you pour from a bottle, air replaces the space where the liquid use to be. Even if you plug the cork back in immediately, the damage is done. That empty space is now fully of oxygen.
Boxed wine solves that problem because the bag prevents oxygen from getting in as you pour. Because it isn't rigid, the bag is able to collapse around the wine, rather than let air in. Unfortunately, until now, boxed wines have fallen into the "mediocre" or even "undrinkable" camp.
Really Good Boxed Wine solves all of those problems at once. It stays fresh up to 6 weeks after opening, 20x longer than bottles, because oxygen doesn't touch the wine. And the wine inside is the same quality as the $30-40 bottle you've been saving for a special occasion.
So what do you do when you want just one glass of wine on Tuesday after work? Do you open a good bottle and risk not finishing it? Do you compromise and open a mediocre bottle so you won't feel as bad if you have to throw it out? Do you say "screw it" and drink the whole bottle? (sorry, tomorrow me).
These problems are now a thing of the past.