There were quite a few years around here, say early 90's til a year or so ago, that we quit seeing scrapers and started seeing the excavators and 'arctics' doing their job. What I understood on the whole deal was that with that combination of equipment you only needed one "operator" for the excavator, and the ones driving the trucks could be, basically, trained monkeys that knew how to turn a steering wheel.
Like I said that went on for awhile until the owners started to realize that having 'trained monkeys' wasn't as good of a money saving idea as they thought. As a result we're seeing alot more scrapers onsite again. Personally I think it's a much better way to move dirt anyway, regardless of the 'trained monkeys' or experienced operators.