We absolutely all need carbs in our diets. Glucose is the first and most efficiently utilized source of energy in our body. You can cut out carbs and force your body into fat metabolism (the basis for Atkins diets, etc) but utilizing ketone bodies as an energy source comes with its own costs. Protein will be the last energy source for obvious reasons (you need muscle to do things like sustain your heart beat! With those ketogenic diets you need to eat a lot more fat which increases LDL levels as well as the fact that your liver is in overdrive producing ketone bodies. Also you’re not getting any nutrients from fruits/veg/grains. Not eating carbs is effectively forcing yourself into the state of a diabetic with total insulin resistance and the inability to use glucose as an energy source. Diabetic ketoacidosis is ugly.
So, there must be some approach to a “lower carb diet” that people are following with preferential sources of carbs.