Because Panasonic over-charges? Looking at this
latest comparison against the G1X (jpeg and RAW files available) here, one is almost forced to believe that.
Do not forget Canon has already indicated they are releasing a MILC system this year. So, the G1X caters to one group of buyers in the interim: those who want to buy a relatively compact fixed-lens camera with the best image quality. And the above link testifies they have pulled it off quite well.
Fast lenses are used when one wants shallow depth of field and/or avoid high ISO. As such, they are good for systems employing smaller sensors such as the 43 and m43 system. But the pitfall is this: they are BIG and HEAVY. The 35-100 f/2 weighs a ton and costs a bomb in comparison to 70-200 f/4 lens on FF and this pretty much negates all their advantages.
Coming back to your original point about fixed slow zoom on G1X vs fast prime lens on GX1, it seems you are ignoring the inconvenience of primes. And you are also forgetting the target buyers of G1X cameras don't really care too much about that small optical difference between zoom and prime lenses. How often do most folks print big these days?
You are obviously a non-Canon user who's really not interested in what they offer; you are only keen on dissing their products indiscriminately.