Proof of absence is not required for lack of belief, and lack of belief in any god makes me an atheist [1]. There's nothing faith-based about it.
There are millions of other things I don't believe in too; it's the default position in many cases.
[1] That's the definition: "a person who does not believe in the existence of a god or any gods" - https://www.merriam-webster.com/dictionary/atheist