Every person does have this opportunity. Many people grow up being taught about god, many people choose not to.
It's not your life that changes btw, it's the afterlife.
65-100 years here on earth vs...
eternity
honestly even from a non religious standpoint what have you got to lose?
There a difference between being taught about God as you say, and being raised with/without God. When you're raised with/without it, there is no other opportunity, God exists/or not therefore you have faith/or not.
When you're raised in a religious or atheist household, the truth is already here and you don't have a word about this, the choice is closed because it has already been made for you.
Being taught about it lets you the choice to believe it exists or not.
Not every parents are this aware of that, most of them just raise their kids following their own beliefs which is completely logical. Not every kid have this opportunity then.
Ultimately, yes, you can choose to change your view but let's not act like everybody is able to change their own paradigm, it takes strength and character and most of the people who are raised some way stay that way. Not because it's the easiest way, but because this is the only way for them.
And it's not about just the afterlife. The possibility of God impacts the your very life : the way tou think, the way you act, the way you interact with people too. Living your life with the idea of heaven/hell will definitely impact it.
But don't get me wrong : even if I think God is human made, that doesn't mean that I negates spirituality. I've already have OOBE's and lucid dreams and I done took some psychoactive substances that sometimes put me into altered consciousness that led me to think that our spirit and our body are entites on their own. And one can "move" without the other.
So, that's why the idea of God is not linked to the "afterlife" in my opinion.