Firstly, sugar substitutes are always more expensive. For the general consumer, price is more important than health, so penny sugar definitely wins. Secondly, substitutes were not always safe, against this background, a strong stereotype developed that these are very harmful substances, which still lives on (in terms of the degree of meaninglessness, this stereotype is similar to the stereotype about the dangers of GMOs). Therefore, yes, today sweetened products can be found only in large stores on one modest shelf. In many other countries the situation is different. I think it's a matter of ignorance and conservatism (especially in terms of nutrition) of Russians.
Apparently because sugar is dangerous only for diabetics, and for other people it is an element of the body's nutrition. And the human body is well adapted for its assimilation. Of course, an excess of sugar is not useful, but the absence of sugar is not good. We need carbohydrates for life, and sugar as a simple carbohydrate is generally a good way out. And a sweetener is just a useless food supplement.