[NSFW] Why did the insult "whoreson" fall out of favour, being replaced by the objectively less elegant "son of a bitch"?

“Son of a bitch” does not speak specifically to the relationship of the mother and father. “Whoreson” is an older version of “bastard”. But a bastard may be a recognized child that was merely born out of wedlock.

“Whoreson” implies lack of knowledge of the father.

Either way it places blame on the mom and kids, while the guy gets off Scott free.

Still being widely used in the Netherlands.
Hoerenzoon.

As well as in Spain.
Hijo de puta.

It’s just the mutability of language over time. To me, whoreson sounds Elizabethan.

My guess is that not all whores are bitches and not all bitches are whores.

I think “son-of-a-bitch” rolls off the tongue much more eloquently than “whoreson.” It’s all in how you say it.

Is there a connection between “whoreson” and the name “orson” (Orson Wells, Orson Bean) ?

I can’t recall ever hearing the term “whoreson.” To my ear it sounds archaic, like “thine.”