It all comes down to cost. New scrapers cost a fortune and they have limited use as well as no one wants to or knows how to run them correctly as some of the other guys have stated. When your digging a borrow pit you spend more time pushing or pulling a pan more than they are moving on there own power. The big excavators and trucks can move more material faster and cheaper than anything else. Besides when it gets greasy a pan is almost worthless(at least the single engine 621 and 631's that are around here). I have seen a D400D 6-wheeler hauling gob from the coal wash plant dragging their bellys through the mud all day long and seem to ask for more. With those capabilities you are able to work in a lot more adverse conditions and time is money.