People dont need to eat carbs to stay alive: most tissues can run on fatty acids and ketones, and the body can make carbs (slowly) from protein.

Dietary fiber is technically carbs, and if a person eats no fiber, his gut microbiota withers, which is bad, but that won't kill him any time soon.

Sorry, let me rephrase - sugars are necessary for a pleasant and significantly healthy life.

Did you mean to write sugars specifically as opposed to carbs that can be used to supply energy to the human body?

I.e., wouldn't enough rice and potatoes suffice?