Sabai,
As Rodman99999 said, Some redundancy is definitely happenning. Regenerators are really a unneccesary cost. All of our AC powered audio devices in fact dont use AC voltage at all.
They are all DC devices so really they need clean DC not AC. So creating "pure sine" is almost utterly a waste of time.
The AC current, after entering our gear, becomes rectified into DC and that is it for the sine. The big electrolytic capacitors accumulate the electrons, these electrons become a source of energy for the active devices in our gear. They are being released slowly as a DC current.
These electrons have no memory of their AC past. They do not remember nor care if they arrived in a form of perfect sine, cosine, square wave, or chaotic ripples. As long as they arrived, their sins are forgiven in the capacitor and they are purified. So in other words, the hi-fi gear is indifferent to the AC shape.