Heaven is supposed to be a prefect paradise where those who go there are in a state of perfect bliss.
But here's the thing, the strongest emotion most people feel is love for their children (there are exceptions of course and that's fine, but still the majority). But what if a parent gets into heaven but his or her child goes to hell? How could the parents possibly experience perfect bliss if their child was being tortured in hell? Wouldn't this be a deeply horrible and traumatic life for the parents? Same for other close relationships: Lovers, siblings, friends etc how could anyone be happy in heaven if someone they cared about was in hell? I ask you Jacob, could you be happy in heaven if someone you cared about was in the lake of fire?