this is actually a great point. Presumably, the top left corner was used because that is the placement for the "back" or "previous" button. Unfortunately, the

this is actually a great point. Presumably, the top left corner was used because that is the placement for the "back" or "previous" button. Unfortunately, the back button was placed there because it is just out of reach for most users to prevent accidental taps. Now that you bring it up, since some of these sliders are actually used quite often it doesn't quite make sense to have these menus exclusively triggered by a button in the top left. I guess it could have also been due to the resemblance to a menu and most "file" commands were traditionally in the top left.