Origin isn't nothing, but it only counts for so many of them for so long, I don't think it has the ongoing draw that test rugby does once they've played a season or two, particularly once they've won it (it's a bit the same with a Grand Final). The fact that our guys aren't winning anything means they're still hungry to try for a lot longer. International league is similar right now, probably with more interest in repping Samoa or Tonga a few times and moving on. That's something they can still do if they go to R360, just in Union instead. I don't think anyone really cares about the Kangaroos (yet) when it comes time to think about contracts.
But overall I think the big reason it's different is because RA is used to being outbid and having to compete somewhat outside of financial terms for their playing talent. In league that has only ever happened in isolated spots and they don't have a whole of game strategy to address a cashed up competitor going directly for their top flight talent. It's also a bit tricky when you've got ~18 clubs running around but only a few guys still get to be the "best" or "biggest name", it leaves a lot more genuine stars with wandering eyes who are open to an opportunity like this.