1) If you research anything about blockchain/cryptocurrency you inevitably stumble into fanatics who shill the project without knowing anything technical. As this is the usual method for the HN crowd to understand subjects it turns them off immediately.
2) The HN crowd mostly have cushy US jobs and as such do not value trustless systems as much as people in other parts of the world. Banking mostly works for Americans and alternatives don't seem to give much benefit.
3) It threatens US control of the international monetary system. Swift, USD etc.
4) The environmental impact of the first generation PoW systems, mostly Bitcoin at this point, is a waste of energy in the mind of HN. The trust and security that it provides to the blockchain is not valued.
5) Many are tired of getting asked about blockchain/crypto by people who have made a lot of money on it, especially if the HN people have not. It has to be a bubble since the tech savvy guys don't believe in it.. right?