That life goes on forever. It's a nice promise. It helps to mitigate the fear of death fear of the unknown. There's just no reason to believe it's true.So, you treat friends and family with care in hopes they will mistreat you? Ignore you? I do not know which denomination you (or your family) followed. You do seem blissfully unaware that many denominations/people of faith follow God's laws because it smooths the way in this life. As far as I know, all Christian sects teach the afterlife is a gift and not a thing can be done to earn it for oneself.The difference, of course, is that friends and family are in the here and now. My actions directly affects those relationships. I don't love my friends and family and treat them with love and respect hoping that will earn me rewards. That was the point of faith (rewards in an afterlife) and the promise of religion in the first place! And my overwhelming experience is that believers find it very easy to believe because the dynamic of the belief system has cultural / geographic biases and it addresses concerns about mortality. It just doesn't back them up with any authority.
Therefore, the teaching that life continues on after death is simply a heads up to be prepared for it to continue. Those who believe in reincarnation caution people to have a care about what they do in the present.
Honestly, though, do you think that forever party in heaven will be any less fun if your eternal ego or "spirit" if you don't attend?