Why do we mourn death rather than celebrate life?

I'd say most people do both. I do.

Grief is the price of love. If you lose someone and it’s not sad, that would be sad.

Animals have no religion but they grieve for their dead.

I wouldn't say that my cat, who is dealing with the recent loss of her companion is "celebrating the fact that he lived at all".

She's pining for him, even though they didn't always get along.

Birthdays are for celebrating life.

You can do both
There's no right or wrong answer

We do both.. like celebrating birthdays is basically celebrating life .. just when someone is gone people realize all the things they never did .. so it’s sad ..

I think it's just who humans are... we all mourn and deeply miss a person we cared about... and there is evidence of that long before religion came about.

We have celebrations of life, I think it's just a thing now, not specific to a religion or this region. What kind of sucks, is everyone is partying except the person it's for. I'm gonna have mine before I go doggone it.

We mourn the loss, it's a natural reaction of most people, regardless the culture or religion. We know we will miss the person and that it's definitive.

No one cares until it’s inconvenient or too late.