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

Explanation

Geostationary satellites have two distinct characteristics :
(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, it can never fly above the polar regions. Hence, geostationary satellites are not useful for studies of polar regions.