If what you say is true, wouldn't we already be seeing incredibly sweet things being sold? I don't see why companies would hold back from producing very sweet products with high sugar content; they do so already.
I'm not sure anyone's clamoring for sweeter drinks. Non-diet drinks like Coke have an established recipe, and diet sodas approximate the same balance of flavors.
I think there is some level of hardwiring limiting the palatability of sweetness, at least in some people.
Anecdotally, even as a kid, I found Skittles to be unpleasantly sweet. To this day, I avoid most sweet soda drinks and seldom drink even those I can tolerate.
It is not discipline for me. It is not even taste. It is tolerance.
I'm not sure anyone's clamoring for sweeter drinks. Non-diet drinks like Coke have an established recipe, and diet sodas approximate the same balance of flavors.