[reikonomusha]

Optimization of code is valuable in a lot of industries where time-to-complete or time-to-react is proportional to money spent/lost.

[keithalewis]

Most of their cohorts just use C++ for that. Several Wall Street firms wrote their own language back in the day. Until the business people figured out IT people just liked to write languages and tell happy stories. They are in the money making business, not the language writing business. Division of labor.

I spent 3 years at Morgan Stanley writing A+ and loved it. A+ is dead but kdb lives on, and is widely used at top hedge funds.