The main reason I played WC WAS for the story, personally. Yes, the gameplay was great but ultimately, the reason I avoided sleep when first playing these games was to see the story progress, not just to kill more furballs.
some system for rewarding the players actions
Yeah I was more interested in getting to the next cutscene, conversation, etc when playing WC. You were driven to want to know what happens next. Oh yeah and killing Kilrathi was also a nice bonus.