Agnosticism is a painkiller for the suffering of a lack of clarity by those who have no interest for various reasons in pursuing it. It justifies to ones conscious their inability to face their skepticism by neglecting their innate curiosity through which they can find truth.
“One couldn’t possibly know” is no answer when one hasn’t hit a wall-so to speak-in pursuit of the answer. Rather it is a way to show unwillingness, disinterest or fear of participating in discoveries made daily, that take us closer to an answer-to-all, by science. Furthermore, it puts the philosophical mind in comatose and gives the individual a false sense of clarity.
Most annoying-to say the least-part of it all is the claim that they know the limits to which human intelligence is bound. To claim that no one can know that a deity exists or not is not only a direct insult to human intelligence but also by claiming that they know humans are incapable of answering a question they haven’t yet failed to, is no different than a claim that there isn’t a god or otherwise.