Direct from amp headphone wires...

A long time ago somebody posted Grado factory wires that were designed to run from an amps binding posts to the headphones.

So 2 questions. 1. is this advisable, why not more common? 2. Anybody want to sell me some?

I am not the most electrically minded. I figure it has to do with stepping down the amps but Apparently Grado had this for there factory production. Should work for public consumption and skip all the headphone amp stuff.
There is an ASL product that takes your amps output and provides a headphone jack and there are also the AKG K1000 phones that are designed to only run off of an amp. The AKGs are discontinued and getting very pricy.