I'm not religious either, but I always find this hard to believe. What are the odds nature happened to provide all the building blocks for us to be here to question our existence? It seems far more likely that (i) nothing would exist, (ii) the universe wouldn't have the right combination of properties and forces to maintain its own existence, or (iii) it would be a boring universe filled with a couple of basic elements capable of producing nothing of interest. Instead, we have complex life and we're here building iPhones and spaceships.
For that reason I can't believe there's a single universe and through coincidence it happened to contain everything needed for life. Even if we go with the multiverse theory and a near infinite number of universes, I still find it difficult to believe. You can argue the universe is filled with a bunch of garbage and we're assigning meaning and value to that garbage because it's us, and we want to feel important. However, I really don't feel like anything (and certainly not something as complex as us) should exist in the first place. I want to say it's too much of a coincidence to happen by chance, but at the same time, I don't have a better answer as to why we're here.
What is so remarkable about the iPhone or the spaceship? Why is it worthy of note when compared to any other phenomena in the universe? What brings you to make a distinction between a live human body and an inanimate celestial body?
I'm not trying to say that humans are more important or meaningful than a rock. I agree with you that nothing inherently has meaning and it's an attribute we create and assign. I'm only saying that we're intelligent beings that are capable of some rather advanced tasks, such as creating a iPhone. In my opinion, it seems far less likely for us to exist than either nothing, or a simpler universe without us.
Yes, it's not impossible, just like I could throw a handful of sand in that air that falls to the ground and happens to write the story of my life. It's so unlikely though that I can't help but wonder if it wasn't just chance that we're here.
It means (pun intended) that the meaning is not self sustaining term in our reality - there is no absolute meaning outside of our perception. There is only relative meaning (as in what kind of meaning my perception assigns to things that can be observed by me - simply put - we create our own meaning).
It can be simplified further to there is no meaning or the meaning does not exist but in my opinion this is oversimplification and reeks of nihilism.
So if You look at things from the point of view described above the "why" question (which can be paraphrased to "what is the meaning") is wrong.
I also wanted to add that it's not that I think it is wrong to ask such questions, only that I think they're wrong when considered from within our system of knowledge, so I find them unanswerable.
Kind of how like "what kind of food does that digital computer like?" is a wrong question.
To cut to the chase: our brains are just piles of chemistry. There is no meaning. We make it up, and that is ok. “Why” we exist is coincidence and millions of years of happy little evolutionary experiments blindly conducted by nature. Maybe there is a Deus ex Machina in there, but for our purposes does it really matter?