It's still used at those companies. Arthur Whitney wrote an APL variant called A+ still in-use at Morgan Stanley. He then left and wrote the "k" language, which is just ASCII APL (although definitely some major differences). K is the language of the extremely expensive kdb+ time series database (normally used for stock price data analysis I think). It's all in-memory data on a giant SSD (very fast and elegant design). He since left kx systems (company he made kdb+ with) and has a new startup called Shakti. Finance are generally the only folks that can afford the prices I believe.