svargino ’py etam icchanti
lokam nirayinas tatha
The residents of both heaven and hell desire human birth on the earth planet because human life facilitates the achievement of transcendental knowledge and love of Godhead, whereas neither heavenly nor hellish bodies efficiently provide such opportunities.
Srila Jiva Gosvami points out that in material heaven one becomes absorbed in extraordinary sense gratification and in hell one is absorbed in suffering. In both cases there is little impetus to acquire transcendental knowledge or pure love of Godhead. Excessive suffering or excessive enjoyment are thus impediments to spiritual advancement.