Because rewarding PCs for killing things or subduing them encourages PCs to go round looking to kill things or subdue them.i admit that my exposure beyond this message board is limited, but I don't see many arguments for this approach. I'm curious to hear your reasons why this works better. (This may require a separate thread)
There is so much wrong with the way XP used to work.
Levelling up classes differently - eughhh
Awarding XP to different players differently - Oh lord no.
Forcing players to start at lower levels when they die - Not on my life.
Xp for treasure - Wow, wealth as a synonym for power isn’t my idea of a heroic theme.