And how do you propose to effect that? Because can you trust apt? Not really, but we just do. Can you trust that you're talking to the DNS server you think you'

And how do you propose to effect that? Because can you trust apt? Not really, but we just do. Can you trust that you're talking to the DNS server you think you're talking to? Again, not really, but we do. Can you trust that your admin won't violate their contract, and the law, for personal gain (or to prevent personal loss)? Still no, but again we typically do anyway. The real world includes things like large infrastructure, hospitals, defence, etc. Separating root from kernel in those settings adds complexity because just having "be root" be your access pass to the everything has already been proven to not be good enough time and time again.