scott_s made an insightful comment about this recently: https://news.ycombinator.com/item?id=7609289.

HN isn't against humor per se. Personally, when I read Reddit, I'm in awe of how good the best jokes are. The problem is that you can't have everything; with a culture of humor comes a flood of lame humor. HN's tradeoff is to optimize for signal-noise ratio, so that stuff tends to get hammered.

There are other places to get lots of internet humor. HN is never going to be one of those, not because people don't like to laugh, but because the signal/noise problem is hard.