Why are geostationary satellites not useful for studies of polar regions ?

Explanation

Geostationary satellites have two distinct charcteristic :
(1) Geostationary satellites are HEO satellites and are placed at 35780 km above the earth's surface.
(2) A geostationary satellite revolves in the equatorial plane of the earth, and thus, not around the polar regions.
Hence, geostationary satellites are not useful for studies of polar regions.