My initial thought was what I replied above. Then when I re-read, I thought I was wrong and had misinterpreted, so I started writing a reply echoing your question: "What makes those things more 'helpful'?"
But in the second article, it's about those careers being more useful towards romance. The paragraph break seems to indicate a slight change of context, so I assume now that that's what this helpful referred to.
So I think a proper decomposition of this gives us:
I'm not sure usefulness has anything to do with the results of romantic priming. The simplest explanation seems to be that STEM careers are associated in our culture with unsexy attitudes and groups: aesthetically uninspiring, analytical as opposed to emotional, attractive to socially clumsy people, etc. If you've got romance on your mind, you're likely to find those associations at least mildly aversive without needing to go into cost/benefit analysis -- and indeed I predict that the results of a cost/benefit analysis, even limited to romantic opportunities, would be a lot less favorable to the humanities.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.