1) Reasonable workplaces wouldn't be bothered if you browse HN while you would otherwise be unproductive (waiting for something to download or compile or load or something).
2) People use SFW/NSFW even when not at work; you wouldn't open an NSFW link in a university lecture hall because it didn't say NSFULH.
It's actually okay for many jobs and workplaces.
if the business I'm at right now doesn't want you using a site they stop it at the network level. This is why I can't get into my Google Drive