It would be like that if you were looking at it decades ago when key sizes were small and cryptographers didn't have much faith in the one-way-ness of hash func

It would be like that if you were looking at it decades ago when key sizes were small and cryptographers didn't have much faith in the one-way-ness of hash functions, or from the perspective of that branch of information theory which seems to permit the existence of arbitrarily powerful computers. A lot of guidance coughman pagescough is still written that way. In the real world, our computers are limited by physics. It seems that in crypto, the least controversial assumption we can make is that given enough secret bits (i.e., entropy) we can be safe from brute force attacks.