The thing is, that everything should have a reason. Without it, those things would defy logic. You could ask the question "Why is this happening?" or "Whats the reason?" but in reality everything has a reason. That thing that creates something must have a reason, and so forth. Get what I mean?
Why does your knee hurt? That is because you banged it on the chair or something else. In a way everything is interconnected to each-other. From your birth to your death every single decision changes your life. If you are a uneducated grownup that is because you you didn't study when you were a kid. Every thing is connected by invisible strings
In the first place, why humans were created (Doesn't matter what's the creation) ? If there is a god and created us, he must have had a reason and as we've read we know he did have not one but a few...
If we were created of evolution then the reason is "evolution" isn't it?
If there was no attraction of the two genders, there would be no sex, if there would be no sex there would obviously be no human multiply...
So if there is not a reason for everything, why did everything happen for a reason? At-least mother-nature works that way, and if we are known to be the creation of the nature we cannot be different.
Not everything is premeditated and programmed into your life to affect you, but everything does in some form. Everything does not happen for a reason, but the sum of everything in one's life shapes who they are and will be. You are what you make of the situations in your life.
A certain reason for any event could imply that there is an intention behind that event. And not all events that happen have intentions behind them, especially not in the natural world. Because we are cursed and blessed with a pattern-obsessed organizer for a brain. One would be advised not to lose sight of the distinction between man-made and natural.
Instead of empirically pointless "why" questions, try "how" questions. Of course, if we had a cosmos-spanning comprehension of all factors involved, we would know the "how", but we can't. Thus we cope with ignorance with logic and deductions that our senses can perceive and shape. A better term than "reason" would perhaps be "reaction", because however the universe came to be what it is, the stuff it contains do nothing but constantly react. That's it.
Logic is just a tool we use to make our lives easier. "Reasons" or "causes" are discovered by observing correlations. Even "correlation doesn't always mean causation" is observed this way when we deliberately create conditions that we've observed tend to go together on their own and notice that increasing or decreasing one has no effect on the other and vice versa.
If everything always fit in with correlations nothing new would ever happen. This means random things are happening all the time, even on a level small enough that we don't notice it in our everyday lives.