Hell's feed

Aren't isekai really pitiful? Like in most isekais the girl who's body was originally theirs is taken away after being sometimes abused verbally, mentally and physically. What happens? They just DIE? Isn't that sad? Like, it doesn't even show what happens to the soul. Why they don't get the happy ending, but the one who got transmigrated into their body is? It's so unfair isn't it?