You do - but religion can be non-theistic. As an atheist, you nevertheless strive towards ideals that have ultimately no reason but your belief in them... That is religion - it is personal and it does not require supernatural beings.
https://www.theonion.com/god-angrily-clarifies-dont-kill-rul...
It's a pretty big claim that ethics has "no reason but your belief in it". There are plenty of logical reasons why one would want to behave ethically, even self interest, beyond you simply believing it.
There are also some moral principles that follow directly from factual matters, provided some very basic first assumptions are made. Theories of just resource distribution and social justice are of that kind. The principles that get things going are very basic, e.g. reciprocity, generality of moral statements, and fairness in the sense of trade/bargaining/exchange fairness get you very far.
It is a myth that religion provides values, as it can be shown very easily by historical comparison that it never has. The values defended by major religions such as Christianity and Islam have changed over the centuries again and again. Modern Christian values, for instance, mostly come from the enlightenment movement and were not endorsed at all earlier. (Christianity is just an example, AFAIK this is true for all religions.)
Churches and 'holy men' have always had a vested interest in selling their values as a product of their religion, though, and they are very good at selling this false story to the public.
Also, for the final paragraph: Your theory of religion seems to be based on intelligent design. I think it is more accurate (and less prone to conspiracy theories) to think of the evolution of religious memes in darwinist terms of "natural" selection.
Not necessarily: https://en.wikipedia.org/wiki/Moral_rationalism
This really isn’t hard. Morality is just goal-based behavior. Paths that lead to a goal are called good; paths that lead away from a goal are called bad. Whether or not a goal is itself good or bad depends on where it lies on a larger path.
So, what are the ultimate natural goals? Easy. One is life, which is the prequisite for being able to make choices; the other is death, where no more choices are possible. Certainly, you can switch between these goals, but the key point is that nature gives no clue which you should choose. Therefore, all natural ethics is based on personal taste.
N.B. In Christianity, something outside of nature steps in and says, “choose life.” That’s why atheists can act morally (search heuristics can end up being similar).
Direct pursuit of the ultimate goals is not efficient, both because it is computationally impossible to calculate what action is most efficient in any situation, and also because direct pursuit will lead to a lot of conflict.
As a solution to this problem, one or more levels of heuristic rules have developed that solve this problem in a social environment, and that form some kind of low-level social contract that we will follow if others follow it. Part of "signing" this social contract (ie be perceived as cooperative), is to bind yourself to the commonly accepted morality. Part of this is that you have to convince yourself that you hold the rules sacret.
Of couse, if you experience radical changes to the environment, it is likely that your fundamental goals will be in conflict with those additional layers, and your behaviour will change accordingly. Most people are surprised of themselves when this happens.
For some interesting points about how these aren't the same I'd refer you to Richard Holloway[1]. An ex-Bishop he has refered to himself as a recovering Christian and writes extensively on ethics. He realised that people could make perfectly good ethically arguments without any reference to religion when he sat on various national advisory commitees whilst Bishop of Edinburgh.