Reloading after a character dies isn't optimal or suboptimal, it's wanting to ensure everyone survives. And unless you're playing on an emulator with save states, most of the FE games I've played only let you save in between battles, so if you lose someone near the end you have to make a hard choice between restarting the entire thing or losing a unique and possibly valuable member of the cause.
I've always enjoyed playing with perma-death. In X-Com for example, I love that i can enable setting so even if I want to, I can't save some one who is dead.
X-COM is different though, since everyone starts out as faceless mooks and you can always get more. In games like FE, every character you recruit is unique and irreplaceable.
I do play a lot of games with perma-death rules, but I can't seem to bring myself to do it in Fire Emblem