Homework Help: Capacitors, Capacitance and Dielectrics

Hi,

So I am learning about parallel-plate capacitors.

The way my book puts it is that it is basically two parallel plates of opposite polarities, separated by a distance d. In order to establish that distance, work must be done and the energy is stored as electric potential energy.

From that description, I understand that the purpose of a capacitor is to store potential energy.

I then learn that a dielectric can increase the capacitance of a capacitor by decreasing the potential difference but, in the process, it diminishes the stored potential energy, according to the equation:

Energy = Q²/C

Why, then, is a dielectric used if it decreases the potential energy (what I thought as the function of the capacitor)? The purpose of a capacitor is to store more charge? There must be a connection I am not seeing.

Can anyone elucidate me?

Thanks!