my biology book told me in school that 1st carbs are burnt,then fat and then protein.
fat is the source only when u need more energy and dont have enough carb.
doesnt mean its necessarily good.
also,carb happens to give maxm amount of energy.
so yes,u need it.
plus it should be consumed(unless u're intolerable or allergic) for thats how our ancestor have evolved.
(remember that chapter evolution in school..our gut's evolved with our brain size!)