He replied with, roughly, "Those of you who work here probably couldn't do anything else other than perhaps math research. Arguably, working here is the economically efficient use of your time."
I think about whenever I see a comment like this. Quant firms select for a very specific set of skills. In particular, I've found that many traders/software engineers in quant are very smart but not very self-directed. Places like Jane Street work well for people who can excel, but only when given a lot of structure and direction. I think this is not unrelated to why so many people 'accidentally' end up as traders after going to an Ivy League school!