People don't understand why you do a DID play through.
The rule forces you to play way more cautiously. You end up doing everything you can to prepare for a wilderness trip or a dungeon crawl, every fight becomes more exciting, you use every single advantage you can to stay alive etc. It's there to make your life mean more, and thus add excitement to the game.
This sums it up nicely. But something you missed, it also forces you to pick your fights much better. The amount of times i would just "RUN AWAY" to fight another day, either because the fight was not looking good once in it, or simply just didnt even want to get involved .
The good things about this type of play, is that it is all up to the player if they wish to do it.