Thanks to @JustKip

[agnostic.com]

Why do we need to synthesize them?

Depending on the definition of "spirituality" you either wouldn't want to or it's a separate issue.

I bundle them all together and file them in the complete bullshit section.

Spirituality can mean anything to anyone. When the term is used it is going to be understood differently by the person recieving the information. Do you mean cosmic magical stuff or emotional internalized zen stuff? It does not matter the person you are addressing will get it wrong.

Atheism is a belief statment. Usually defined as a lack of belief in god/gods.
Agnosticism is a knowlege statment. Usually understood as I do not know if there is a god.

Spirituality is the joker in the deck that can mean anything much like the term God its self.

I believe it is best to keep these very different concepts and answers to questions in thier own catigories and to avoid conflating them.

Why would I want to?