So I get what you're saying, but this isn't my experience. There's no room to use small changes in volume for expressiveness at the low end of the volume scale

So I get what you're saying, but this isn't my experience. There's no room to use small changes in volume for expressiveness at the low end of the volume scale, since attacks/sustains/release shape is more quantized. So if your piece has fff and ppp in it (which is probably a full 40dB range) the ppp part will sound super flat while the fff part might sound great.