[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.