Compare the storage capacity of ATP and glucose

ATP is generated by the body through metabolism so it can be converted into a variety of tasks within the body.

Glucose is an alright storage mechanism but it is not preferred for long term storage because it is polar so water surrounds it so it can not be densely packed. (this is why fat is used for storage of energy, it is non-polar and can be stored in adipose tissue).

So all in all ATP is in equilibrium with ADP and AMP in the body, and when your body needs energy to do tasks like movement, it uses up more ATP so there is more ADP and AMP so your body goes "time to break down more sugar!" and it digests glucose (contained as glycogen in the liver primarily).