HN seems to be very tech community, yet security and things like CTF which do require proficency and experience in both - theory and practice doesn't seem to be popular here
But even without knowing the answers to those questions, in general I've found that anything that requires significant amounts of both theory and practice tends to have a very small potential audience, and HN is no different in that regard.
CTFs are security competitions between teams coming from many countries.
Those are some of "topics" that challenges/tasks during those competitions do cover: (stolen from dev.to)
Cryptography - Typically involves decrypting or encrypting a piece of data
Steganography - Tasked with finding information hidden in files or images
Binary - Reverse engineering or exploiting a binary file
Web - Exploiting web pages to find the flag
Pwn - Exploiting a server to find the flag
Generally it requires to be very proficent at CS and Computers in general to compete at highest levels
HN has very wide range of audience from differnet domains(business, biology, physics, maths etc etc). Pentesters/Wannabehacker is just one of the small groups. HN community really reflects guildline -
> On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.
What you're looking for is very specific domain. In HN's context 'Hacker' doesn't mean only security domain but The Hacker Attitude (from this - http://www.catb.org/esr/faqs/hacker-howto.html) which could be applied to any domain.
(b) Why do you think it's not popular?
But even without knowing the answers to those questions, in general I've found that anything that requires significant amounts of both theory and practice tends to have a very small potential audience, and HN is no different in that regard.