If you only get one life, and can kill other players, what's to stop somebody connecting as TROLLAXOR BINLADEN and just teamkilling 24/7? Because if I was 13yrs old that's what I'd be doing.
2) When you spawn, you have very little in the way of equipment. You have to dig through abandoned houses to find a lead pipe, much less a gun. You wouldn't be able to kill an established player.
3) Following from 2), people would catch on and kill you quickly.
It's certainly possible, and people certainly do it, but griefing in DayZ is really unrewarding. You wouldn't be able to do it without a huge investment of effort.
Second, you start off with no resources. It would be pretty silly to play long enough to get enough resources (guns) to kill someone only to throw yourself at anyone and everyone you see, considering each attack would diminish your resources and they are likely to try pretty hard to fight back and kill you, at which point you'd have to start over.
It might be fun, but it would get tiring quickly I think
As in, most games the jerks are twenty somethings.