I can back you up on this Bryce..
In my area, just outside of Chicago (25 min train ride) I see the sparkling waters at Walgreens, and the Big Supermarkets, but not so much at the convenient store type places.. 7-elevens are fewer and further between in my area, and I would usually make these kind of purchases when I am getting gas, but there was only a brief stint where I saw spark ice at my local convenient/gas shop..
I always see the brands fully stocked while I am grocery shopping.. I do notice the FruitWater's are disappearing and not being restocked in all the flavors..
I wonder if I will see VitaminFizz at my local grocery store.. That might change my view point..