Essentially, C++ is popular because of existing code, particularly proprietary third-party libraries. And you are correct; even HFT shops will use languages other than C++, which is why anyone who's actually worked in this industry will know that the answer to the question of popularity is not performance.
And that's why I hate that SE question so much. It was asked by someone outside the industry and is mostly answered by people outside the industry.
Comments
Here's the question that should be featured on HN:
http://quant.stackexchange.com/q/306/35
Essentially, C++ is popular because of existing code, particularly proprietary third-party libraries. And you are correct; even HFT shops will use languages other than C++, which is why anyone who's actually worked in this industry will know that the answer to the question of popularity is not performance.
And that's why I hate that SE question so much. It was asked by someone outside the industry and is mostly answered by people outside the industry.