the left-right slidey things were an Apple affectation, no doubt introduced just to be different, after all, Apples were for the rest of us. We're different.
they have much less usability
what stinks about them is you can never quite figure out or remember if you're supposed to just tap, only tap on the "other end", or actually slide the slider.
FWIW, the ones on iOS have always been something you could drag. As far as I have ever understood, all of the UI controls on iOS were designed to be skeuomorphic in a way that directly made sense for someone futzing with their fingers: you push buttons, you scroll a WHEEL to work with selection boxes, and flip switches to toggle options (which also, notably and at the time almost specifically on Apple products, take place immediately with no concept of "Apply", and aren't part of a "form" metaphor).
they have much less usability
what stinks about them is you can never quite figure out or remember if you're supposed to just tap, only tap on the "other end", or actually slide the slider.