I look at it as a what sells
kinda thing. Think about how many companies, farm workers and the like use these coolers. In the morning I meet around the ice machine with a 100 other workers shoveling in ice at the water trough only to repeat it the next day. Add that during a hot day most of the crews drink 70% of the water, or usually want fresh water every day (sure sometimes I just throw in more ice), having a cooler that holds ice for a single day is fine. Look at a Yeti cooler...very thick and doesn't hold much for its overall size then add to additional cost and most companies wouldn't want to spend that much. Oh crap, my 200 dollar water can is rolling down the highway. The friggin crankster's were stealing mine at least every other month from in front of my house at dark so I had the shop build a padlocked vault around the thing. I'd be in deep ---- if it was an expensive cooler.
You could always go the Fabergé egg route and put a little one in a larger one
Huge but don't hold much.
But I'll bet there is some kind of space age material that would work better to insulate; it would just cost bucks cause only a handful of people would probably want such a thing. No demand for the price I would think.
Then on the other hand maybe you could make something and become a millionaire
I've seen some high dollar lab stuff that might work for you just don't know where to get such a thing.