I don't care about realism, I care about the fun my group is having. People sometimes forget that the goal of the game is to have fun, and that different people have fun in a different way. Does the threat of PC death help your players having more fun? If so, good for you. It is not the case with my group, however. We don't like to worry or fear for our PCs.
I personally made the experience that I play very differently in a game where I have to fear for my PC. I play more "efficient", less concerned with fun and style, instead focusing on tactics and minmaxing. I am also more prone to rules lawyering in order to avoid my PC getting harmed. All these things I do not consider conductive to a fun experience at the gaming table.
As a DM I don't kill off PCs without a warning and a way out ("Do that and you may/will die. Want to reconsider?"). I don't want a game focused on tactics and survival, but a game focused on character interaction and style/panache, where players can play characters as if in a movie (or sitcom/soap, in some cases).