Don't worry, both AMD and Intel do get that.
I believe AMD set the idle clocks to 800MHz on their CPUs because setting them lower makes sod all difference to power consumption but instead just makes the machine feel less responsive.
Most of the saving comes not from the underclocking, but from the undervolting that underclocking allows. So, if AMD feel that they have a minimum voltage they dare run and stay reliable, and at that voltage the CPU can safely do 800MHz, then that is the idle speed.
I think when the Phenom range came out AMD said the volts & clocks can be set independently on all cores, though I don't think my motherboard does that. I do notice in Linux my machine quite often has one core at 3.4GHz and the others idle at 800MHz when running a program though.
The next step is to dump a core's CPU registers into some ram and shut power off entirely to that core to eliminate the static leakage power. I think Intel may already be doing some of that, AMD are certainly putting it in upcoming models.
AMD Llano stuff on Anandtech talking about clock & power gating