If you are referring to the "Hacker" part, I guess it makes sense since this is a list of books referred in "HackerNews".

If you were referring to why Karpathy's name was invoked in the post, piggyback effect I guess?

Like how people talk about “Uber for x”? There’s probably a whole bunch of benefits - a vague sense of already being familiar, a quick understanding of the underlying similarity if you’ve done it well, a halo effect, etc.

I’m not sure where you get your evidence for “never get more popular than the original”. I’m sure you just haven’t heard of the originals that faded away.

Describing things by reference to other, similar things is sort of how language works. Humans aren't quite Tamarians, but denotative meanings do often derive from connotations that originally attach via metaphor, analogy, or other forms of comparison.

Obviously _some_ users are better than _no_ users on your app.

Some reference to something known is better than no reference.