I didn’t take that to be his point. I assume he says “economically efficient” because he means their strongest skillsets don’t have (m)any other uses and they wouldn’t be realizing their potential by leaving those skills unused.

He probably overstates that case, especially talking to early career interns that haven’t yet narrowed their specialization and could pivot to other highly quantitative roles that use other high level math.

He’s also probably flattering his audience, to whom “math research” is more likely to be status-bearing.

Doubt he’s saying they’d suck at anything else.