The fat is valuable because it’s energy without insulin. Protein and carbs have insulin responses but fat has an almost insignificant response.
Since there is a limit on daily endogenous fat usage, not consuming enough energy ends up reducing metabolic rate. Eating other macros raises insulin and locks up endogenous fats even more. Fats also achieve satiety faster. They also improve immunity and are protective against old age illnesses.
So the fats just solve so many problems … did I mention I love my fats??