It seems a coke-sized can, requires only 13mg of this protein, compared to 200mg of aspartame.

If brands see that increasing the amount also increase sales without increasing the risk - they're likely to do that - which could numb the sweetness of anything else.

These are both very small amounts of a substance, relative to the size of a Coke can. I think if Coke wanted a sweeter formula, bumping up to 250-300mg of aspartame or using a blend of existing additives or something would not be a problem for them.

Given how sensitive consumers are to changes in its taste, I think the overriding concern for Coke would be not changing the flavor of the formula.

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.