It's not just about mortality. It's also a justification for morality (no T).... among other things.....
For me, G-d is very unlikely to be found on the pages of a book. For me, the Bible is very unlikely to be anything other than the words of man, though sometimes it is about what man thinks of G-d. I think it's folly to say G-d wants us to act in some way, and not some other way.... and I'm given very little comfort believing that my life is simply some sort of "test" laid in front of me by G-d..... where I have to choose to believe what I regard as a ridiculous and internally invalid story or face eternal damnation....
But, those remarks, to me, don't ever really address G-d at all. In my mind, there must be a creator. I can't say I have "proof" of this "must" but, for me to make sense of the very simple fact that I exist... that this universe is here... I can't see any sensible alternative. Sensible to me, that is... I can't wrap my head around there having once been nothing, and now there is very clearly something which allegedly was born of that nothingness. So, I believe in a creator... but... I can't tell you what this creator thinks about things like honoring your mother and father... and, actually, it seems to me quite silly he'd have any opinion about it one way or the other. MAN has a vested interest in obeying such a command.... G-d? I can't see why he'd care at all. What difference would it possibly make him?