Averaging over categories of wildly distinct things is misleading. It's like taking average temperature of all human bodies in the hospital and judging public health by that measure - ignoring the fact that some of those are dead bodies in the freezer and some are running high fever. Or, another example, if you look at average wealth of people in a pub, and Bill Gates and Warren Buffet walk in to have a pint, the average wealth would jump up, but nobody really became any richer. Conclusions made on this kind of measures make sense only in specific conditions, but when we could a huge expensive car as one thing and 1000 tiny toothpicks as 1000 things and averaging over that, it can not help but being misleading.