On the one hand, that's true. But just the act of dying is itself traumatic, I imagine, and that must have the potential of giving returnees PTSD from Hell, given how much PTSD *not* dying can give the rest of us.
There's also been more than a few hints that at least *some* mutants do not trust the resurrection protocols. At one point, Rictor is dying of a disease from one of the Horsemen, and suggests just letting him die and coming back in a disease-free body and Apocalypse freaks the **** out and demands that he fight to survive, rather than allow himself to die and be resurrected.
One the one hand, that's *totally* in-character for Apocalypse and his survival-of-the-fittest ethos, that he'd despise the idea of 'giving up' and not fighting till your last breath.
On the other hand, he's absolutely fine with *other* mutants (like Gorgon or Melody Guthrie) dying and coming back. It's only when it's someone like Rictor, who, for whatever reason, matters to him, that he is willing to endanger his own life to try (refusing the Morlock Healers aid and ordering him to help Rictor instead) and keep Rictor from dying and being resurrected.
Storm seems similarly hesitant at first to accept Callisto's request, and Kurt, IIRC, has seemed a little squiffy on the process, despite having gone through it himself!