Character backstory - Better Source DM or player?

[Reversefigure4]

But then we're back to Batcathat's point; that kind of player will want a reason why they are going into the meatgrinder in the first place.
Also, this might just be me, but the meatgrinder as described by TemporalTravles would kill my immersion quickly; why do new characters show up suddenly whenever one of us dies? Where are they coming from? Why do we trust them? How do they know we need a replacement? And if they get sent by whoever sent us, why didn't we take them with us right from the start?

In this meat grinder setup, there are dozens and dozens of undefined people already on the battlefield (or in the dungeon, or the gladiator pits, or whatever) who are already your fellow adventurers/soldiers. You're not playing a character, you're playing a faceless pawn to see which one survives long enough to develop a personality. Bringing in a backstory is actively undesirable at this point since your pawn likely won't live long enough to call on it in any way.

There's certainly nothing gained by doing this backstory-wise over "you're all survivors of the orcish massacre on planet Auxin, who now work for Inquisitor X".

I guess it's fun for people who don't want backstories but like meatgrinders? It's fairly specific.