[bsimpson]

The Go S appears to only have one rear button on each side.

I've played half a dozen games on the original Go, and I don't think I've used more than one rear button. In Half Life, it's more comfortable to hold for crouch. In one of the Spider Man games, it expected a trackpad click, which was easier to perform with a rear button.

Since games have been designed to be playable with only the face buttons, there's not always obvious utility for extras. Maybe as premium controllers become more popular, this will change. For now, I can definitely see the argument that 4 buttons are superfluous (except for standardization).

[MoreMoore]

Just because everything is bound to the face buttons doesn't make it the best solution. Developers make do with what they have. Extra buttons mean I don't have to move my finger off the trackpad or joystick every time I want to do a common action, particularly while aiming the mouse cursor.

[rtkwe]

I do enjoy the back buttons even on games that were originally XBox controller games, those are relatively cheap compared to the trackpads.

[philistine]

Back buttons have turned me from an inattentive nincompoop at Dark Souls to a true Souls head.