[kasey_junk]

Now admittedly this is sampling bias, but I have never seen code written by a quant that could be put into production without being reworked by a software professional.

The skill sets are in some way exclusive of each other. Quants do lots of exploratory work. This involves tons of one-of experiments and throwing away things that don't work. They often frequently don't have the operational understanding of the way the systems they interact operate. Further, making stuff fast on a computer is a very, very particular skill. People that could do all of that are extremely rare (such that I've never met one).

[vasilipupkin]

Sampling bias. At least in HFT, the days of hiring quants who can't code are over.

[lucozade]

I can personally vouch for the fact that there is a large space between "can't code" and "write high performance production quality code". Quants are no exception.

[gjm11]

And a large space between "can't write high-performance production-quality code" and "doesn't write high-performance production-quality code".

I can write high-performance production-quality code, and occasionally I do, but maybe 95% of the code I write is hackish, primarily intended for exploration and experimentation, and written in a language fundamentally ill-suited for high performance. Engineering it all carefully and optimizing it would be a tremendous waste of time and effort.

I work in technology rather than finance, but I bet there are plenty of quants for whom much the same is true.