Because nobody cares about Hunter Biden himself. Nobody is invested in him like they are in a president, he's not really a "public figure". He only exists as this character somewhere in the void that people mention every now and then, he's not the same kind of public figure that the Trump kids are, for example.

It's not a story like "This nice, well-spoken young man who I see on the telly all the time did cocaine off of a stripper's bare tits? I can't believe it!"

It's more "Biden's son who's known for doing coke and fucking prostitutes did coke and fucked prostitutes again, go figure."