If you compare the Sony/Zeiss lens price to what I've used in Nikon and Canon, the Sony is actually cheaper. Also, the lens options for the A7RII is less (by far) when compared to other cameras, but for what I do I'm not missing anything. I mean, what lenses are the actually missing for 90% of photographers? I have a 55, 35, 90 Macro, 70-200, 12mm Fisheye and 15mm wide angle.......and that's more than I probably need anyway.
You can also use just about ANY lens from other companies with the help of an adapter. My wide angle lens is from a different company and I'm using a Wolf adapter with it and it works perfect.
As far as the why goes, the camera is flat out better in just about every way for backpack hunters/photographers.