I think it's a combination of that and colonial superprofits keeping most workers in the imperial core just a little bit too comfortable for them to risk it all in a revolution.

That's not to say that the labor aristocracy wouldn't be better off materially under socialism; it's just that the circumstances aren't quite dire enough to motivate a direct revolutionary conflict with the imperialist state.

This video from Hakim on the subject is really good and offers a tangible response to the problem for parties in the core (i.e., support third world revolutionary movements as a priority):

https://www.youtube.com/watch?v=4lDZaKjfs4E

But yeah, also propaganda.