I'm really confused as well. HN is not really a community and there isn't even a set subject on this site. People who are interested in Tech news? That would be an absurdly broad and uninteresting classifier.
Can you imagine a Slashdot meetup? Could potentially work at a combination circus-firing range-porn addiction support group, all taking place in your Mom's basement.
If a HN meetup could someway or another uphold that level of quality, it could be a great conference even if the topics are as varied as deep learning - to web frameworks - startup culture - to UBI economics.