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.
Yea, I have no doubt that there are still a handful of extremely well paid APL devs at the company I worked at then (I wasn't at morgan stanley). I was part of a project that helped put a webservice frontend in front of the app so that non-power users didn't have to use a cli to interact with the application if they didn't want to. I don't think there was any appetite or desire to engage in a re-write due to the risk involved when I was there then and I would guess they have maintained that reasoning. I have a vague recollection of some of the stories from the APL devs, one of them was the first to get APL working on a personal computer way back in the day. He carried the computer into some APL conference and demo'd it and got a massive ovation supposedly.
I worked at a company right out of college that used K for some things. They did some consulting work for the financial services industry early on, and I think that's how they started. I ran through some basic tutorials, but never worked on any of the projects that used it, so never became proficient. Only a special subset of blessed people got to use K.
The only things I remember are that a symbol could could do 3 things when used with a monad, dyad, or infix, and that it was very hard to read anyone else's code because it was so terse.
They also went through a phase of naming their Java classes things like com.a.b after getting used to K's terseness. Fortunately, that didn't last very long.
