It’s the broadcast standard in, at least, the UK and US.But HLG is not that popular. Only one HLG channel on Youtube. And anyway, it is even harder to present. And somehow everybody does not understand that HLG has SDR layer that should be presented on SDR displays and instead color manage HLG laywer. Hillarious.
It’s not “popular” for recorded content because it doesn’t add as much value there, but that’s really irrelevant.