I've emailed corporations in the past with stupid questions like "Why the heck would you promote chromium in your beverage on the label"? The answers I received were not very satisfying.
I'm imagining in my head a wiki entry for "The Missouri Pacific Cider disaster" where in 1993, Martinelli's finally shipped its first experimental 2-gallon containers of sparkling cider. "While in the process of being shipped to stores across the US, a train with 23 boxcars of cider hit a bumpy set of tracks, shaking the cider to pressures beyond which the bottles could hold. The resulting explosion destroyed a large section of Argyle TX, just outside of the Dallas Ft Worth area. ..."
Yeah, sometimes my imagination runs wild.
An argument is two people sharing their ignorance.
A discussion is two people sharing their understanding, even when they disagree.
It's probably a marketing idea. If it's $2.50/700 mL bottle or thereabouts, then a 2 gallon container would cost close to 10 bucks or thereabouts and at that price, it wouldn't be very attractive to consumers.