Why is energy conserved?

that is the answer, and is pretty much the only answer anyone will have to offer you. think of it this way: if energy wasn't conserved, where would this energy come from? if you dont eat, you die. because your food stores high amounts of energy which your body transforms into the energy required to keep itself alive. if you stop eating, you die because your body can't create energy. neither can anything else in the universe. this is essentially the universe' way of telling us that there's no free lunch. we can't pull something from nothing. think of the way matter is conserved. i can't simply reach up into the sky and pull down a cheeseburger simply because i decided i want one. this extends to say i can't reach into the air and collect energy from nowhere. everything has to come from something else.