Really? You want me to give you a "Scientific" reason?
Alright! I'll try! Let's consider the scientific method:
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That's a very basic representation of what the method is like. In our case, the question would be "Is Islam legit?". Basically, our job is to try and ascertain the truth of the claims Islam makes.
That brings us to the next phase. In this phase, we "Collect Data". How did I do that? Well, I've checked what claims were made by Islam and what evidence were provided to back up those claims. The result was that a shit tonne of claims were made without any good evidence to substantiate them. That's a very awkward thing to deal with scientifically. This isn't an Islam only issue. Virtually all the religions I know about have this problem. Let me give you some details on what we have to deal with usually:
· Baseless Assertions
These are just claims that are stated in the holy books and we are supposed to accept them as facts. Statements such as "It is Allah who does X!" or "Allah made this and did that". As a scientist, one cannot accept claims, especially extraordinary ones, without evidence. That isn't allowed in science.
· Un-falsifiable Claims
Many Islamic claims, similar to various other religions, are unfalsifiable to begin with. If there is no way to prove or disprove an assertion, why should I accept that as true?
· Signs of ignorant human origin
When you take a look at the content, whether it is about the legal system (Shariah), the testable claims about the world or simply the method of delivery of the message, it smells strongly of the product of ancient ignorant barbarians, not any hyper intelligent divine source.
In order to avoid duplicating content, I'll link you to my answers where I have provided details on these issues. For example, the Qur'an fails horribly when you test it's claims about the real world ("If the Qur'an has scientific facts, why don't atheists believe in it"). The inhumanity, violence, bigotry, misogyny etc. that the Qur'an preaches is just what you'd expect from a book authored by backward inhumane people without any regards for human rights ("How can someone read the Qur'an and still remain a non-believer?"). As for the method of delivery, what kind of an all-powerful intelligent being do you think would rely on sending yet another book to mankind for guidance? Not only that it's one book among many such books, there is no way to trace it's content with certainty even back to Muhammad, let alone his God! The all-knowing omnipotent God decided to choose the same method of delivery that the other supposedly "fake" religions and charlatans use! The message is so important that he made it indistinguishable from the rest. Not to mention that he picked a language that even the majority of the Muslims don't understand.
· Suspicious Tactics
The claims in the Qur'an often come coupled with threats. Usually, when a scientist discovers the truth about a matter, they submit their evidence/test results for others to examine. Then their peers review their work and when others can independently verify the claims, we start accepting that as the truth. In the case of the Qur'an, instead of providing us with any good evidence, it jumps straight to issuing torture threats for those who don't believe. That is a very suspicious method of persuading people which is generally observed only among people who themselves know that they are lying and the only way they can get you to accept their claims is by intimidating you.
Conclusion:
Basically, if we were to develop a hypothesis (Stage 3 from the top in the image) that the Qur'an is yet another man made book, a product of its time and the place it originated in, it'd test positive for it. If we were to test for any signs of divine origin, it'd test negative for it. Which forces me to conclude that a belief in the divinity of Qur'an is unjustified.
