Is a trench necessary for camping on the slope? Why dig a trench?

[Manti]

From their last photos, we know they dug a trench.
However, was the tent even found in a trench? From the search photos, it doesn't seem so but hard to tell.
I have read on a different site that a searcher said a trench was found next to the tent but can't find that testimony in the case files...
What could be the purpose of digging one? Starting a campfire perhaps?

[Paf]

It is probably not a trench, but just a plateforme.

When you want to camp on the snow, you can not just set your tent on top of the snow. It's not hard enough, even if it's crusty and not to thick ; the tent would fly away at first wind. (plus, your body weight would form a hole in the snow under the tent : and sleeping in a snow hole is quite cooler than sleeping on top of an even, solid layer of packed snow - or on frozen ground.)
Plus, they probably wished to have a horizontale bed, not a steep one !

[Manti]

Yes but there were areas very close that are almost horizontal, they could have just pitched the tent there.

And a little slope is no problem as long as you're lying with your head up.

[Paf]

I think they choose the spot to be protected from the wind (even assuming there was no wind when they set it up, they didn't want to be surprised ! They knew what a ridge is).
That explain also why the snow was so deep at this place : the snow is blown from flat surfaces and carried away to and deposed where it's calmer, creating snowdrift. It's like 10 minutes digging, not a lot of work (on the picture we can actually see somebody putting their backpack down : what we see was dug by the first hikers to arrive, before the last one did), but it's a lot of confort.

[Игорь Б.]

Дятловцы поставили палатку на ровной площадке, где не надо было копать снег.

Фотографии раскопа были сняты не на месте палатки:
http://1723.ru/forums/index.php?s=&showtopic=5133&view=findpost&p=75302

Это место их не устроило или из-за большого камня под снегом или (что более вероятно) из-за надувания снега на скат палатки:
http://1723.ru/forums/index.php?s=&showtopic=5133&view=findpost&p=64481

P.S. Место палатки было найдено в 2013 году с точностью 1 метр:
http://1723.ru/forums/index.php?s=&showtopic=5133&view=findpost&p=63482

[RidgeWatcher]

In Alaska I have always witnessed a trench, for several reasons, even though I havenever dig one myself but I watched.

1) Trenches even the ground, if you have ever slept on a tilted projection it is not restful.
2) It blocks the wind.
3) It blocks a possible mini land-slide
4) If you are going to start a fire or cook, you need a trench and preferably a snow or ice wall for protection, considering you whether you cook inside, like the   Dyatlov skiers did, or not.
5) A trench with a mountain side wall can also protect from snow drift.