Dump pouches are expendable lightweight bags used to store expended magazines, malfunctioned equipment, and other unneeded things you don’t want to leave in the field.
Yes. All militaries require their soldiers to return expended magazines and other disposable equipment if in any way possible both to reduce material costs and for tactical reasons.
While not an essential part of your equipment, a dump pouch will allow for several important strategic and tactical benefits. It will reduce your mission cost and make tracking you harder.