On reddit (for example), the jokes, puns, and sarcasm clog up most threads, and it's hard to find signal in the noise.
HN has far less noise and is a better use of my time. It's the only community with as much density of information in the comments.
There are lots of funny sites and I bet HN users visit/enjoy them. I think a lot of us want one place without jokes.
Another issue, of course, is https://en.m.wikipedia.org/wiki/Poe%27s_law
HN’s guidelines communicate that it’s meant to be one of those places, and so people who appreciate that may downvote, flag, or chastise things even when they do find them funny.
The kind of joke that can only derail a perfectly good post and conversation is well avoided here because once you hit the cynical "huck huck" post, the rest of the thread is meaningless and devolves further and further until people finally stop responding to it, and there is no longer any interest in reading the other threads.
There are times a humourous observation, quip or quote is exactly what the doctor ordered. But online, that is nowhere near as common as the very tiresome "huck huck" type that nearly always can be interpreted as "my self-assumed humour is more important than what this post is about" or "let's ignore the post altogether and just regale in my self-assumed sense of humour instead!"