Since radio waves are comparatively large, it is easy to achieve good angular resolution with even a small radio telescope compared to optical telescopes, making it easier to pinpoint a potential source.
The atoms and molecules in this range are components of water, so wavelengths in this region may be chosen for communication by other civilizations.
Atmospheric emission backgrounds are small at these wavelengths.
Galactic emission backgrounds are small at these wavelengths.
Compared to other portions of the EM spectrum, radiation at radio wavelengths travels with a minimum of absorption by interstellar gas and dust.