Hi JohnQ,
Good question. What you’re describing is having a “dominating layer” on top, and many people prefer this feel, as it offers a bit more of a “crisp” surface comfort that’s a little less point elastic. As the uppermost layers of the mattress receive the most specific compression and use, having a more durable layer above the softer layer would extend the life of the soft layer beneath the firm dominant upper layer.
There’s a bit more detail about dominant layers in post #33 here.
Phoenix