It MAY be true that a user would want to fly a big expensive aircraft at or near its payload capacity, but the reality is that that is seldom the case in the real world for either fixed wing or rotary wing aircraft, especially military cargo aircraft. From the C-5, to the C-17, to the C-141, to the C-130, all carried average payloads far below their max payload, and that is equally true of the CH-53, CH-47, CH-46, CH-3, V-22 and others. Military missions are far too diverse to enable the users to fill the aircraft to anything near their capacity. Further, many (most) military missions "cube out" before they "gross out", meaning the cargo hold volume is filled before it reaches its payload weight capacity.
As for wide CG envelope, when you're under fire or about to be under fire, it's very nice to be able to load up quickly and take off before taking the time to calculate the CG. This is done routinely all over every theater of operations in which the US and its allies are engaged. A wide CG envelope is also very helpful when doing sling loads. The CH-47's three sling load hooks and wide CG envelope provide a very flexible external load capability.