There's another way to look at it.
But first we have to understand what death is, in game terms. And for that we need to understand what life is, too.
Simplified: life is a state where the body of flesh and muscle and bone and other tissues is animated by natural life-force, spirit, soul, whatever you call it (as opposed to being animated by ooky necromancy kind of unnatural means). Then death is the state of removing that life-force from the body, whether done by damaging the body so much that the life-force cannot remain there, or using magic like death spells to simply kick out the life-force.
Now that is really simplified, but that's a basic gist of it.
Where does that life-force go when it leaves the body?
Well, sometimes it doesn't go far. Ghosts, revenants, etc., stick around and haunt places and seek revenge on their killers.
But for everything else, it goes off to its happy hunting grounds, heaven, elysium, bytopia, the abyss, wherever is most appropriate.
OK, then at low levels, heroic PCs can't really do much about this. At paragon levels, PCs are starting to really get around, but are still mostly limited to the material plane and their home world. But at Epic levels, the PCs are out boogeying all over the multi-dimensional universe, visiting other worlds and other planes at will, coming and going wherever and whenver they please.
It seems a bit unjustified to say "Yeah, you can go to the abyss, or bytopia, or wherever, and you can visit your dead friends and companions and family, but you can't do anything to bring them home with you."
Sure, you could rule it that way if you want to.
But, in a game where everything else is possible, where players can level mountains with a gesture, then replace them with new mountains with another gesture, putting barriers between them and their dead companions, especially when they are standing there looking at their dead companion's spirit, seems arbitrary.
And ruling that "The gods won't let you take him back" is also a bit arbitrary, but at least believable - except that D&D provides for PCs killing gods. Assuming the PCs are powerful enough to engage and defeat gods, telling anyone with that kind of power that they can't do something like restoring their dead companion gets really arbitrary.
All you have left is "because I say so, so nyaa nyaa, neener neener."
So why not just make mechanics for it and avoid the whole "because I say so" mentality?