A chassis holds and supports "things", e.g. engines, transmissions, cab mounts, and so on. It is not part of the suspension. It is the back bone of the vehicle, literally and is an un-damped, uncontrollable spring. Talk to anyone who builds or tunes race car/truck suspension and I guarantee you they will each tell you the same thing. Additionally, they will likely also say they prefer the stiffest chassis possible, i.e. carbon monocoque or a tube chassis, so the suspension can do what it does best, suspend the vehicle body, follow the road, maintain traction, put the power down to the ground to avoid tearing up the trail or sending the vehicle flopping over.
The fact that you aren't racing, going fast, rock crawling or building a hyper car is of no matter. The design parameters are conceptually identical. A frame is not suspension; that is what links, bags, dampers, coils and leafs are for.