This seems a completely strange question.
Artificial sweeteners exist because people pay money to consume them. This is because currently, the economy is dominated by market capitalism, and businesses get a profit form selling consumers products.
Artificial sweeteners exist in the market because people want to eat sweet foods while also not consuming so many calories that they get ill (immediately).
I personally avoid all artificial sweeteners religiously. I wish they would disappear due to the ill health effects on the masses from their consumption. However, I can understand their appeal given that I *love* love love sweets. I have straight up beet sugar or vegan ice cream regularly, or very sweet bananas with sugar, or dates, when I want sweets.
I can't stand spicy foods, but I love sweets. It seems really strange to ask "why do people want sweets when I don't want any". I dislike tea, but when I do I put in at least 5 to 10 spoonfuls of sugar in it. To each their own.
The market works in insane. (part of the reason I don't favor it universally)
"The worker has the right to leave his boss, but can she do it? And if she does quit him, is it in order to lead a free life; where she will have no master but herself? No, she leaves to sell herself to another employer. She's driven by the same hunger. Thus the worker's liberty is only a theoretical freedom, lacking any means of realization; an utter falsehood."