Actually the radiation belts are a negative side effect of the earths magnetic field as well as the Suns magnetic field. As cosmic particles collide with particles in the atmosphere they decay into energetic protons while the outer belt is mostly electrons made in geomagnetic storms.
if it didn't exist we could launch more satellites or have larger space stations without the worry of perpetual radiation exposure as for earth there would be no negative consequences to the loss of the energy.
