Someone told me that in Israel, a dead body is buried directly in the ground with no coffin. Why do they do this only in Israel, and use coffins outside Israel?
Note: Rather than phrase the question "reversely", your answer can be phrased this way if you can cite a source that the original halacha or minhag was to bury without a coffin, and the idea of coffins was used later on, historically. If so, please provide some historical context as to when coffins became more common.
Shulchan Oruch Yorei Deyoh 362 (1) says
הנותן מתו בארון ולא קברו בקרקע עובר משום מלין את המת. ואם נתנו בארון וקברו בקרקע אינו עובר עליו, ומכל מקום יפה לקברו בקרקע ממש אפילו בחוצה לארץ.
Someone who puts his deceased relative in a coffin and does not bury it in the ground transgresses the prohibition of delaying burial. If he put the relative in a coffin and buried it in the ground, he does not transgress; but at all events it is better to bury the dead directly in the ground even outside the Land of Israel.
So the best way to bury is without a coffin and that is why this is done in Israel.
It is assumed that the law outside Israel requires a coffin but The Natural Death Centre reports that
Contrary to popular belief, it is not a legal requirement that a coffin or casket must be used to house a dead body. The only legal stipulation is that 'It is an offence to expose a dead body near a public highway as this would outrage public decency'. A body should therefore be covered in public, but the method of doing so is entirely up to the individual responsible for the disposal of the body.
There are movements around the world for Natural Burial.
How excellent a thing it is, therefore, both for the righteous as well as for sinners, when their bodies are in close contact with the earth so that decay can set in quickly and their punishment may not be prolonged through the continued existence of the body; for there is not one of the righteous who can escape the judgement of the grave,
ועל דא כמה טב לון בין לצדיקי בין לחייבי, למהוי גופא דלהון דביק בארעא, ולאתעכלא גו עפרא לזמן קריב, ולא למהוי בקיומא כל ההוא זמנא סגי, בגין לאתדנא גופא ונפשא ורוחא תדיר (בכל יומא), דהא לית לך כל צדיק וצדיק בעלמא דלית ליה דינא דקברא,
for the angel appointed over the graves stands over the body and punishes it daily. בגין דההוא מלאך דממנא על קברי, קאים על גופא ודן ליה בכל יומא ויומא,
And if the righteous have to undergo this judgement of the grave, how much more so the wicked! אם לצדיקים כך, לחייבים על אחת כמה וכמה,
But when the body decays, the judgement ceases in both cases.
ובזמנא דגופא אתעכל ואתבלי בעפרא, הא דינא אשתכך מכלא,
