When someone dies........?

Why are people so sad, especially if they are christians like my parents? Shouldn't it be good... like a celebration? I mean life is horrible,,,and they believe in heaven( which is infinitely better than life). Unless they think that person deserves to go to hell, they should rejoice. Why are the being so selfish, I mean it's not like that corpse can feel any pain( it's abiotic). When they say... they've gone to a better place( while crying), I think it's a little hypocritical... and that they're only fooling themselves, but nowhere is still better than life on earth. What are your opinions?