Nerve density isn’t mainly about intensity, it’s about spatial resolution. More nerve endings per square centimeter means you can distinguish finer details of touch, texture, and pressure. The brain can’t invent spatial detail that isn’t in the incoming signal. Amplifying a sparse signal centrally would be like zooming into a low-res photo.

The brain does do some of what you’re describing though. The somatosensory cortex gives disproportionate space to certain body parts (the sensory homunculus). So there is central amplification, but it works on top of peripheral density, not instead of it. Without the dense nerve input, you’d basically have an on/off switch instead of nuanced sensation.