it's just that random spectators don't really appreciate the subtlety in things like deciding when exactly you build farms & get horse collar and how it ties into attack/defense. they don't understand the decisions about saving for castle/imperial vs making more army.
What i really liked about dreams' commentary was that he would notice all these intersting economic decisions that the players made and discuss their implications, whereas a lot of other casters just talk about the map early on then focus on the fights
It's because I think he came from bw / sc2 first. I have an easier time following his line of thinking because I came from there, too. If he came from aoc first then, oops!