Here is my take from using the devices as my job. The interface on the QC is cool. But here is my issue. On a gig, in the studio, whatever the situation playing music, it is very hard to bend down or even see/change a setting on a floor device. It is nice, but really doesn't change the quality of the sound - isn't that what you really buy a processor for? The sound?
Now having said that - I am all for a better computer interface - because that is a real way you can manipulate the setting on a device like this. I think if you have something like the QC on your desk you can do lots of quick changes, but then loose the function of the footswitches. Same with a kemper. It is seems fractal is looking at it from a "complete" budget/build model. What would be the most useful features knowing there is a limit....
I myself talked about buying a QC - we have one here in the studio, but again, like the kemper, unless you have an arsenal of effects/amps/cabs/etc. the box sounds are "ok" and so what you end up with is something that is ok with a cool interface. And if you use just that one amp all the time, then a QC might be the way to go - but that still means the interface doesn't really matter all that much.
Let's be real for a minute...when is the last time L6 updated their cabs?? QC has cool switches but no software (yet). Kemper is a pro device, just that the software is not so great....so this might answer some of the whys to your questions.
Again, as much as many non-pro players buy these devices, really in the end, they are designed with a professional in mind. There are companies that take a different approach like Brand L6 for example and that is cool. And if that is your thing, go for that.....
There are less and less companies providing working players the real tools they need without a lot bells and whistles that don't get you too far, and I am happy fractal has stuck to supporting us that way....