It’s more than a gentle euphemism — Scripture treats it as an accurate description of the actual state a person is in.

Look at how deliberately John 11 handles it. Jesus first tells the disciples, "our friend Lazarus sleepeth; but I go, that I may awake him out of sleep" (v. 11). The disciples take that literally and reasonably — "if he sleep, he shall do well" (v. 12) — so John explains that Jesus meant something else, and Jesus has to spell it out without any figurative wrapping at all: "then said Jesus unto them plainly, Lazarus is dead" (v. 14). Sleep here isn’t a soft way of avoiding the word death — it’s Jesus’s own description of what death actually is.

Daniel 12:2 uses the same picture for the future: "many of them that sleep in the dust of the earth shall awake." Paul does the same thing repeatedly for believers who have died — "them which are asleep" (1 Thessalonians 4:13-15), "them also which are fallen asleep in Christ" (1 Corinthians 15:18), calling Christ "the firstfruits of them that slept" (1 Corinthians 15:20).

The image fits the reality precisely. Someone in dreamless sleep experiences no passage of time and is unaware of anything happening around them until they’re woken — which lines up exactly with Ecclesiastes 9:5, "the dead know not any thing." That’s why Paul can call the resurrection a waking (1 Corinthians 15:52, "we shall be changed, in a moment, in the twinkling of an eye, at the last trump") rather than a reunion of a soul with a body it never actually left. The sleep language isn’t decoration — it’s the Bible’s consistent, literal description of what death is like for the person experiencing it: an unconscious rest, ended only at the resurrection.