I have always considered "agnosticism" as a form of intellectual nihilism....why? Because the logical endpoint of the "I dont know" philosophy is the necessary admission that you dont really "know" anything with any certainty. It is essentially leaving the door open for the existence of some sky-god, in the complete absence of any evidence for such an entity. Why deny what your empirical sense of logic tells you?
Why are there no "agnostics" for Santa Clause, or the Tooth Fairy or Leprechauns? There are ALSO socio-cultural constructions with no more or less evidence in support of their existence as there is for a "god" in the sky. Does the agnostic shrug their shoulders and answer "I dont know, maybe?" when asked if the Tooth fairy exists? If not, why not?
I suspect many agnostics are simply "mid-way" between the final acceptance of a godless universe, but still cling to some emotional "scrap" of belief because of the warm-fuzzy sense of existential comfort the idea of an afterlife gives them.