I think the older I get it is about the fundamental point - "what is the meaning" of my life. I believe in a God, just not religion. But I do not go to church or follow the bible, and do not believe a God has a direct impact on my life so I cannot technically call myself a Christian.
I suppose strictly I am an Agnostic. I just replace God with "life" in general I can accept that as I can feel myself breathe and see life around me. I think my fellow humans can be kind and generous but they also have the capacity to be unkind and inconsiderate to others. Even completely arseholes and self centred and sadly just evil.
It has never been a straight forward concept in my head.
You can be spiritual, without being religious.
You can be religious without classifying yourself under any organised religion.
I suspect that for many people - more than would admit it - being areligious is a fairly passive process.
Start off believing, and going to church etc; then without really thinking about things, stop believing, but maybe keep up with old habits, and eventually maybe give up on the old habits; but haven't really thought about it, so still consider themselves religious because they've just never questioned things.
For others, it's a case of thinking about things, being bothered by the inherent contradictions in all religions, or learning more about the world and deciding there can't really be a god, learning about logical fallacies, and seeing how no religion can stand up to that sort of scrutiny, or simply thinking that belief in 2600 (known) gods are self-evidently silly, so why is belief of the 2601st self-evidently truthful? - for whom being areligious is an active decision - and are far more likely to describe themselves that way (though possibly not publicly).
As for Pascal's Wager, and in the words of Michael Palin "God would see through such a cheap trick" - and they're not religious, they just describe themselves that way on the off chance that they're wrong and god exists, but doesn't exist enough to spot their fakery; and, of course, that they've picked the right religion to pretend belief in.