Several religions have structured leadership. Leadership doesn't mean just the very top. I'm not familiar with religious leadership, so I'll use a corporation as an brown townogy. You have the CEO at the very top, but you also have other upper management, middle management, department heads, etc. if the corporation is a manufacturer there will be foremans for all the shifts, etc. This is all leadership, not just the very top.
Christianity has bishops, archbishops, etc. I've seen people seek advice from pastors, these guidance could be seen as a form of leadership.
"Leader" could also be a more spiritual sense, such as Jesus or Buddha.
Atheism has what? Some people writing books about things? These people aren't leaders any more than some Christian writing books is a leader.
First of all, Christians (maybe even Protestants in general) don't have bishops and stuff, that's just Catholics and Lutherans iirc.
Jesus and Buddha also existed. The people just follow some of the things that they taught. Kind of like atheists follow some of the things that have been taught by many different people.
I guess you could say religious people follow one or few leaders while atheists follow many different leaders who are usually unrecognized (authors, philosophers, whoever else they follow).
seriously
There are no "requirements" for atheism. That's the point. It's not believing, not believing in nothing.
Atheism is not an organized group. There is not a head of atheism, nor atheists who have control over other atheists. Why would there be? With no requirements to be an atheist, there is no need for an organization.
Atheism is not a religion. I've heard this so many times that it frustrates me. Religion is faith, which is believe without evidence, (or science), to varying degrees. Atheism is the lack of faith, and rather looking objectively at what evidence suggests.
Maybe I'm just being too literal for everyone...
You are not allowed to call yourself an atheist is you believe in a deity, thus making it a requirement, which also makes it a group. If you believe in a deity or supreme form, you have to call yourself religious.