It is very much to do with this Christianised view of Greek mythology. The Greco-Roman underworld was a very different place to the Christian vision of Hell: It was a gloomy, mournful place - in some senses, a dark reflection of the upper world - and while it could be a place of punishment (see: Tantalus, Ixion, the Danaides, Tityos, Sisyphus), its landscape had very little in common with the fiery landscape of the Christian Hell (the only place fire comes into play is in the river of fire, the Phlegethon). And indeed, the underworld could be a happy/peaceful place for those who lived virtuous lives and were received into Elysium or the Fortunate Isles.
And I think people are prone to simplifying the Rape of Persephone - they think of Hades as the evil creature of darkness who stole away the young maiden and condemned her spend half her days in the Underworld. What many fail to understand is how the Rape of Persephone can also be seen as a story of initiation and coming of age - indeed, many of the motifs in that story are reflective of the ancient Greek wedding ceremony.
One can't apply the Christian concepts of "good" and "evil" to these ancient myths. Neither Hades nor Zeus is a clear-cut positive or negative figure.
Hades was a fearsome god to the Greeks, who were in no rush to visit his realm, but of the three sons of Kronos his behaviour was perhaps the least objectionable. In some accounts of the myth he was genuinely in love with Persephone, and having married her he never strayed (although he did lust after Minthe before Persephone put a stop it) - whereas Zeus and Poseidon were notorious rapists who were frequently unfaithful to their lives. And he was a fair ruler - somebody else mentioned his trickery in trapping Theseus and Pirithoos in the Underworld, but that was only after they tried to kidnap his wife!
And Zeus, for all that he could be cruel, violent, inconsiderate, narcissistic and unfaithful, also displayed genuine heroism in overthrowing the Titans and rescuing his imprisoned siblings. He was the god of law, order and fate, and in this role he is capable of showing wisdom and foresight.
But again, there's this Christian mindset that leads to simplification - in Zeus, the sky father and king of gods and men, people see God and assume that he must be good and virtuous; and in Hades, lord of the underworld, they see Satan and assume that he must be purely evil.