Atheist believe they don't have any obligation in this discussion to bring forward any proof. How often do you see a atheist say "You say there is a God or Gods, prove they exists". Well, what are the obligations if a atheist comes forward to a theist or deist and says, "There is no God" and we ask "Well what is your premise or what are you bringing to convince me your position is correct?" The burden of proof shifts to the person making the claim, atheists often wish this was not the case, that they can say "Well, the problem of Evil is what provides evidence that Gods dont exist" or "Since I was born, who gave birth to the gods?"
First off, good for you for looking into this subject of what you believe and WHY.
It's not easy to grasp who bears the burden of proof in the discussion, so let me see if I can explain it.
A common error (which you avoided doing, BTW) is throwing all atheists together, which is a MAJOR source of confusion on the topic, since not all atheists make the same claim: some say, "I believe God does not exist" ('hard' atheists) and there's those who say, "I don't believe God exists" ('soft' atheists).
Look at those claims closely: one is making a claim that God doesn't exist, and thus bears the burden of proving the claim; in contrast, the latter is saying they don't believe God exists, since essentially they haven't seen sufficient compelling evidence to adopt that belief, since they'd say the theist hasn't met their burden of proof! Note how the latter doesn't say WHAT they believe, they're saying what they REJECT.
As an example to illustrate, I'm going to type some random characters on the keyboard:
So I ask you: do you, SLOTS, believe "oibfuismstyeds" exists?
Of course not, since you've never even heard of that word before, and hence it has absolutely no meaning to you. And even putting aside the fact that I just told you I randomly hit the keys to make up the word, you can pretty safely decline accepting to believe in oibfuismstyeds, since you don't even know what it is!
And if someone came to you and wanted you to believe in oibfuisstyeds just like they do, you'd reasonably demand they present some compelling evidence BEFORE you become a believer, too, since it's not rational to believe in things without any proof of their existence, right?
But now the question arises, could you take the extra step to make the stronger statement, "'Oibfuismstyeds' don't exist!"?
You'd have to do some work of finding evidence to support the claim before you tell others that oibfuismstyeds don't exist, since you'll bear the burden of proof to support that claim. You'd have to spend time Googling, reading books of the subject, research the history of those who believe in 'Oibs' (man, I picked a long made-up name, LOL!) to find out how the belief evolved, learn whatever language it was derived from, look at the archaeological evidence from the native land, learn of the ancient culture, etc. If "The Book of Oib" existed, you'd want to carefully examine how it came to be, and see if the evolution of the story of 'Oibs' contained any clues. You'd need to do that, if you make the stronger claim that 'Oibs' don't exist, since that's where the belief of the believers arises.
You can go through the same exercise for theists, considering the implications of those who tells others, "God exists" and the one who says, "I think or feel God exists (or I DON'T believe God does NOT exist (i.e. they reject the 'hard' atheists claim, so default to belief, since that's usually the way they're raised), but I don't make the claim to others since I feel I cannot meet the burden of proof".