The Master of Orion,
Well, that's one possibility. Nuclear weapons are not the only weapon of mass-destruction, chemical and biological also qualify. All could technically wipe out a civilization. WMD aren't the only technological development that could cause a civilization to destroy itself, four such examples I could readily think of could include: Internal combustion engines; Certain industrial chemicals, both of which could cause severe pollution resulting in massive loss of life or even extinction (An extreme case, but possible)
; Artificial intelligence that ends up destroying the civilization that created it; Self-replicating nano-technology that ends up consuming all life and anything consumable on the planet that could feed them.
Other possibilities include society dying off for reasons that are not technological, such as plagues and famine, and insufficient reproductivity.
There is a possibility that we're simply the first planet to evolve life as evolved as primates and humans.
I like to think of it like finding a dozen cats in a forest as large as the surface area of the earth. Scatter those cats in there randomly and then take a few steps into the forest. Will you be shocked if you don't find them after a few steps in? Take five or six more? No cats? Hmmmm...must be a paradox. We know they are in there, so why aren't we finding them? Scale this up by a magnitude of a few billion.