It's important to remember that the Kemper as it is now isn't the end point, it's one step along the path towards the end goal of affordable and accurate emulation of classic amps.
There will be other tools out there, there will be updates to the Kemper itself.
For me the current state of the Kemper is fantastic for the studio and all the reasons PETERFR. stated. But it's not there in other ways. There's no natural room sound/verb, when played through a guitar cab the sound seems to lack the headroom and poke of a real amp which seems to distort differently with different frequencies and have a different sort of "bloom" (sag) effect, especially Fender amps have even without a reverb a certain sound that the Kemper doesn't, almost like they emphasis that neck pickup position sound, to me on clean the Kemper just sounds like different EQ pedals on a dry signal, or maybe going through a not very lively amp more geared for high gain, you all know the ones where lead is amazing, but clean is just dull as dishwater. Some amps have a sort of plosive woofiness the Kemper can't do either, a breathy transient.
Some of it may be just those few precious dB during transients where a real amp peaks with substantially higher levels than it's sustained output, some of it may just be the sag modeling needs some refinement, there could be a million reasons. But the Kemper isn't there yet for me in non studio situations, and it could do with some improvements when it comes to clean sounds and it's rectifying emulation IMO.
It's still the best piece of guitar kit I ever bought though. No regrets.