"Nach" is a very natural choice for the topic of inquiries. Why? Because it's the preposition that goes with "fragen", which is the default/generic verb for that action.
Ich frage nach dem Weg.
I ask for the way.
The ideas of "nach" and "for" are not that far apart. "nach" means that something is behind something, "for" expresses that something is heading toward something. In a way, the only difference is context and if the something is moving or not. Just compare the English phrases
I am coming for you.
I am coming after you.
They're both essentially a threat, only that the second version has a notion of the other person trying to get away.
Generally, you should never think of English prepositions, or prepositions in any language for that matter, as a blue print. The English "for" is just as messed up and incoherent as the German "nach". If you ask "Why nach" I could just as well ask "Why for?". No language is more right than the other. They're all crazy in their own right. You need to get a feel for the general gist of a preposition and then have an open mind for how to use it. The more you try to pin it down the less you'll get it.