How important might this concept be to the Space Marines? These supermen use some of the best, and the rarest equipment that the Imperium can make, and the Imperium is often illustrated as having limitless space, people, and resources, but still a crippling inability to create many things in mass quantities. Certainly the most important thing for a Space Marine squad to retrieve is fallen Battle Brothers' gene-seed, which the Apothecary does, assuming you have one, and not sure, if you don't, but what about the rest of the gear? I never see the Space Marines hauling their dead over a shoulder, to do whatever it is they do with the bodies of their lost, or even just pulling empty power armor, but in a world with so much "respect the machine, and will protect you", if you loose guys, and DON'T bring at least their gear back, that seems a bit of an insult to it, the BB's home Chapter, and the TPs. Do they grab and go, or have some other force sneak in later, and rummage through the dead?
What about Chaos gear? One could argue it's old and tainted, but components are often rare in 40k. Could they use it? Would victorious Chaos claim Loyalist suits, to ucorrupt, use, and strip for parts, or leave it?
In the end, the main question is, I guess, how much value do the Space Marines REALLY put into their gear?