What is it that compels an editor to do it? A lack of early footage that would hook an audience? The idea that putting a promise of something big up front gets people more invested? Those seem like fair reasons.... but what is the cost? I guess you kind of have to take it on a case by case basis.
First of all, this is not decided on by the editor. This is the will of the director and/or producers. Sometimes it's in the script that way already. The worst example I know is Carlito's Way. Brian DePalma felt it was important to view the film knowing what happens at the end of Carlito's story, so he has David Koepp open his script with the end, emotionally gutting the film.
Compare it with the opening of Gladiator, which reveals that Russell Crowe is on a quest to get back to his family. Since his family is slain, the only way to return to them is to die himself. Ridley Scott doesn't make this explicit, but he implies it with a repeated shot of hand thru wheat. You know the film is getting to an explanation of this moment but there's still the voyage of discovery the first time and an extra layer when you re-watch the film.
On one of the DVD commentaries for the TV series Alias, they talk about JJ Abrams having the idea that the best way to hook the audience right away is to open with the most exciting moment of the episode, use that as the initial tease. Anyone who remembers the show may remember that starting with the back half of Season 1, more often than not they would do this. Putting the promise up front.