Saying that someone has died is nearly a taboo phrase.

Euphemisms often surround death in the modern world, where there is a belief that modern medicine can or at least ought to extend lives indefinitely. Once death was always nearby. Many children never made it past infancy and few people made it beyond their forties. Until the 19th century, bodies were buried in graveyards next to church grounds. When burial grounds were moved to the suburbs, they were relabeled as cemeteries, literally, sleeping places.

For those who believe in an afterlife, it makes sense to speak of ‘passing.’  The body has passed from one form to another, from one location to another. But ‘passed’ doesn’t necessarily imply a theological position. You can pass from existing to non-existence.

‘Passed’ has primary come into common use not because of a thought out theological or philosophical position but because we try to protect ourselves from the cold facts of death, the not being the person that we once knew, the sentient creature that constitutes what it is to be a human being.

Euphemisms soften the hard blows of reality and people are entitled to their comforts. But there is also something to be said for looking things straight in the eye.

My own preference is to call things as they are. When my cat suffered from terminal cancer, my family chose to end her life. She wasn’t put to sleep. We took the responsibility of ending her life. We killed her as an act of mercy.

Our society tries to hide from the inevitability of death—just think of the money spent on medical bills the last month of person's life. I think it would be better if we accepted reality for what it is. However, having said that, I can also imagine in a culture in which death was so readily accepted that life itself can be too easily diminished as a value in and of itself.

http://www.psychologytoday.com/blog/am-i-right/201411/no-one-dies-they-just-pass