We believe in an afterlife because we want an afterlife

I think many people are extremely averse to feeling their lives are to no ultimate avail and that the Universe has no purpose and just exists by happenstance. Equally it is repugnant to people and that they will cease to exist forevermore when they die.

I agree with atheists/materialists that this is why most of us believe in an afterlife and God. We want it to be true so we believe it, although deep down I feel many of us don't really believe it.

The mistake here though is to imagine that just because someone believes something because it makes them feel better, then it is false. There are compelling arguments and evidence to reject materialism and all that it implies.