Death and teleporters

So I don't know the fictional science behind teleporters. But the basic concept I got is it breaks you down and relocates you else where and puts you back together. What is stopping them from when someone gets hurts on some misadventure from using the teleporter to fix the damage based on the outgoing data. Like oh when this guy left his leg wasn't missing let's put it back. Or this guy was more alive when he left let's fix him and bring him back. I mean cases like pike if you can completely disassemble a body into components atoms and put it back together, you should be able to fix it.