they put the little cones out for the novice groups to look at and get a feel of where they need to be. (apex's) however, in the instructor/racecar group we tend to turn them into targets. You score more points if you can move a apex cone with out flipping it over.
The bigger cones are just merge cones from hot pits to the track.
Also, Not too many autocrosses have elevation changes, off camber turns, or 110mph front straights. :)