To date no PC in any of my games has ever opted to be Cleric or Paladin. In general, they haven't even been terribly concerned with the gods, but this doesn't mean the gods aren't concerned with them. As Terry Pratchett wrote, "...Gods like to see an atheist around. Gives them something to aim at." While few of the PCs have actually been atheists (a difficult thing to be when gods manifest in front of your very eyes), they have generally been agnostic and not very curious.
I use the Greyhawk gods for humans, as the game is set in my own version of Greyhawk, and Forgotten Realms gods to fill in the demi-human pantheons. Whether the players care to follow any particular god or not, the gods are often involved heavily in the plot of my games. My recent long running campaign is entire based on the awakening of Tharizdun under the guise of the Elder Elemental Eye. The PC, after terrible trials and the realization who the real enemy is, has (for the first time in the player's career) found faith. In Pelor, to be exact.
Long before I knew anything of Greyhawk or Forgotten Realms, however, I had created my own microcosmic world that used a mix of my own gods and those of the Hollow World.