I don't know that it's a universal yearning for spirituality (many, many people are not spiritual), but rather just a very real and human curiosity about how we got here, and what happens to us when we die. What is the meaning of life, etc.
They're burning questions, that we've theorised on 'til the cows come home, but that we're only incrementally closer to an explanation of, than we were 1000s of years ago.
God is just a way that we try to explain it all to ourselves, before we realised the earth wasn't flat, that we're just one planet of many in a vast solar system, and that we evolved over many years instead of being created in a week.
That's not to say we weren't created by a some sort of being - we might have been, but the story cooked up and penned down as the Bible probably isn't accurate.
All we all really want to know is how we got here - I personally think that's what drives us to come up with explanations, rather than a need for spirituality, per se.
I don't necessarily believe in a 'soul'. But to my mind, having watched someone die, I think it's kind of significant that when a heart stops beating, the body remains. What's not there any more, is the very essence of the person - their personality. Or what more spiritual people might call their soul. That's no longer there, and the face of the body instantly looks different without that essence in it any more.
The body remains, even after death. Where does the personality go? Lots of people will say it just vanishes. And great if you feel so certain about that (though you can't know it).
I think we are slowly and only recently beginning to realise how important our mind is. That it needs care, that a mind that has been nurtured since childhood is in good stead for adulthood. That our minds can get injured, hurt and sick, just like our bodies can. And we ignore that (personally and socially) at our peril.
I think our human minds are way, way more susceptible to hurt that our bodies are. Our bodies are - relatively speaking - much more resilient than our minds. But until very recently, no-one cared about people's minds, in spite of most people trotting off to church every Sunday. Mental health just wasn't even a thing.
It's our minds that need friendship, support, kindness, learning, education, and it's our minds that are driven by a need for spirituality or an explanation of why we're here.
I'm really not explaining this very well as I can't even quite get my own head around it, but this is what makes me agnostic, I think.