Hades always was depicted as cold, stern,and he was in charge of death which is hateful to everyone.So people would not worship Hades as much as they did another Gods.
http://www.greekmythology.com/images/mythology/hades_3.jpg
But I think this idea is unfair to Hades.He through the drawing of lots to became the God of Death.It was fated him ,he did it,but it bent him in some way.Hell is a place that is dark、bleak and gloomy.It’s a forbidding place that nobody wants to go there.Hades lived forever with alone in the hell,so he desired to have someone can accompany him.He used improper means to make Persephone became his wife who just stayed with him for three months.Hades loved Persephone but he is a “terrible”God.The special status made he had loneliness stays forever.
Hades was a fair God who gave all his subjects equal treatment in regards to his laws.He hates to be cheated and will punish those who cheat death.I think he was a admirable God.