Can someone explain to me WTF is the Steam Machine controller?

[Mythmaker1]

richardhutnik said:

Mythmaker1 said:

I'm a bit confused. Each home console controller allows you access to only four face buttons without taking both thumbs off the sticks.

With the two buttons on the back, and two on each side of the controller, the Steam controller allows the same number of buttons while still keeping a thumb on the pad. Or is there something that makes the back buttons wrong for these game types?

The Steam Box controller takes the four buttons on front on the right hand side, and spaces them evenly on the left and the right to make them not work the same way.  They do look like they keep the same buttons on the back, but the front is missing the buttons on the side.

But what's wrong with the two new ones on the back? I mean, why can't they fill in for the ones that were moved?