Yesterday was about the aspect of Haides that I liked the most and today is the flip-side of that; it is about the aspect of Haides that I find the most problematic.
Although I like how Haides is Kind and Just, I find that he often seems to be sad or depressed. He is the only one of the Undying Theoi other than Thanatos (Death) who is constantly in contact with the dead. Even Kore/Persephone is only enthroned in the Underworld for part of the year.
This is (if you will pardon the pun) a grave responsibility and unlike his brothers and sisters, most writers do not grant him a golden throne on High Olympus. I would think that this is something that contributed to the sense of loneliness that compelled him to seek a bride to be enthroned with him.