8 oz cans and bottles for soda?

While at the grocery store stocking up for superbowl sunday I noticed a new (to me at least) trend with soda. The return of new shapes of 8 oz bottles and cans. I am truly curious about the history of this return of size. Is in theory because people can't drink 12 oz or is it supposedly a diet thing? Soda in bottles went from 12 oz can to 12 oz bottle to 16 oz bottle to 20 oz bottle to 1 liter bottle. Then of course you could always buy a 2 liter bottle, however few have that as a personal size. Now all of a sudden it has started back the other way back down to 8 oz. I would love to know the marketing thoughts behind this current move.