Missing Simulator Devices in Xcode
Bluntly put: "view as" ≠ simulator.

Those "view as" options are to preview different viewport resolutions with storyboards and are independent from simulator selection. As the resolutions are common with multiple devices (ie. iPhone 6 = 6s = 7) it is unnecessary to list them all. You could think of it as a visual preview.

The device list next to Play/Stop is the actual simulator selector list and choosing one will fire up an actual simulator when running.