I think the disconnect here is that for much of the world these days, "ordinary" programming is a backend for a web or mobile app, using REST (or maybe GraphQL

I think the disconnect here is that for much of the world these days, "ordinary" programming is a backend for a web or mobile app, using REST (or maybe GraphQL if you're avant garde). I'm sure Jane Street does lots of web stuff too, but I haven't see a bunch of Core libraries to do, for example, a CRUD app on Postgres in the cloud somewhere.