It makes for a much more interesting game, where actions still have consequences, but not the same consequences every time. Being seen is a greyer affair, which opens the game up rather than shutting it down. Dishonored ebbs and flows, gracefully treading between action and sneaking without ever lopsiding into either. Stat fiends can still load up every time they get made, and action buffs can charge in if they like.
Instead, I got to be myself for a change. I got to play a game how I wanted to play it, instead of how I thought I should be. If someone struck me as evil, I killed them and didn't worry about the extra quest they might have offered later. If the guards caught me, I killed them too.