Reading about ancient Greek religion and touching upon Hades, he seems to me to be some kind of "untouchable" and not in a good way, when it comes to Gods. People seemed to stay away from him and not mention him unless in some serious dispute. His position is more equivalent to devil of abrahamic religion than God with the way he is treated. Temples to him seem to be extremely rare.
Why is that the case? Why wouldn't God of Death be the chief among Gods? After all, we all die, and would go to his realm, so why not get good with him? Maybe ask for a longer life, or perhaps a better place in afterlife etc.. Yet that is not the case. And a lot of other polytheistic religions that have a God of dead, death etc.. seem to not give him too much of regard.
Am I too influenced by Abrahamic religions, which seem to be all about the afterlife and life after death?
EDIT:
Also, how exactly would people in ancient Greece react if you told them you worship Hades actively, or more than any other Gods?
I would like to add, in addition to /u/carrabaster's magnificent answer, that the Roman equivalent of Hades, Pluto, was much more respected and revered as he was also the god of wealth and all of the minerals in the earth. In Rome, Pluto was a bit more of a God of the subterranean earth and all that it contained.