I used to learn languages "just because", for that very reason: new paradigms and approaches open our brains a little bit you can "bring back" stuff to use in the day do day (Haskell excluded, I gave up long ago :D).
I have to admit I do it less nowadays, mainly because I have less time and because I am more selective I guess.
This is not an issue of merits but (for example, and please Java devs don't take it personally) I don't see myself learning modern Java unless it's required for something at work (which never happened so far). The last time I used Java I was in university.
This doesn't mean I think Java is garbage, on the contrary, it's just not my favorite language and I don't have enough compelling reasons to do it (less so that Google is endorsing Kotlin and Dart for mobile dev). Same goes for other languages.
Over the years I cultivated my Python niche I guess (I had a job involving C#/.NET for a while but that's a story for another day :D): when I started using Python it was seen just as a "scripting language" (which I felt it was a compliment in disguise) by many people and only a few companies in Italy were using it "for real". I kid you not, in the country we probably all knew each other online or in person or at least knew of each other. Every Python developer was on the "python-it" mailing list :D Now Python is so widespread that the salaries are actually going down :D.
Elixir is even in my bio on dev.to, that's how much I like its premises, but I never find the time to actually learn it and use it :D It's just a wish for now, derived from my love of Erlang and declarative programming.
I'll just wait for someone on dev.to to write about it :D
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