Tibetan sky burial, jhator, gives the body to vultures on a designated site, the corpse prepared by a specialist so that the birds can complete the work quickly. It is the ordinary funeral for most Tibetans, not an exotic exception, and it is done for reasons that are both practical and doctrinal.
The practical reasons are hard to overstate. Much of the Tibetan plateau is above the treeline, so fuel for a pyre is scarce and expensive, and the ground is frozen or thin over rock for much of the year. Cremation exists in Tibet and is largely reserved for lamas and for those who can afford it, which is itself informative.
The doctrinal reason is that the body, once the consciousness has departed, is a container of no further use, and giving it to living creatures is a final act of generosity. That framing is genuinely held and is not a rationalisation of the practical constraint, but it is also not the whole story, and accounts that present it as pure symbolism while omitting the treeline are giving a partial picture.
Two cautions. First, the rite is not open. It is conducted for the family and the specialists, photography is unwelcome and is now regulated by the authorities, and the descriptions that circulate most widely in English were produced by visitors who were asked not to produce them. Second, the practice was suppressed during the Cultural Revolution and permitted again from the early 1980s; its present legal position in China is one of tolerance under regulation rather than of right, and Tibetan communities have had to negotiate for it.
The Zoroastrian practice of exposure is a genuinely comparable rite reached from an entirely different premise, and the two are frequently confused in popular writing. Tibetan practice gives the body away because it no longer matters. Zoroastrian practice exposes it because it matters a great deal in the wrong direction, being a source of pollution that must be kept from earth, fire and water alike.