I've pretty broad (if sometimes shallow) interests. I try not to have narrow interests, and I like to learn.
But working on translations, I've learnt bits & pieces about 20th century sculptors and what drove the creation of their art. About railway privatisation in Britain & what a shitshow it was. I now have some knowledge about composite materials designed to withstand extreme temperatures. Recently, I've translated a few books about stage magic.
None of that I'd likely study on my own.