Why do cells use ATP
instead of using the energy
directly from the food?

Cells do not use the energy from oxidation reactions as soon as it is released. Instead, they convert it into small, energy-rich molecules such as ATP and nicotinamide adenine dinucleotide (NADH), which can be used throughout the cell to power metabolism and construct new cellular components.

i'd say that the moon rock is about 2.2 billion years old.