For those that do it often (1-2 years), there are few things more enjoyable for a software engineer, than learning a new programming language.
I started learning Rust this week and was again reminded of the nice and warm feeling you get from playing with a new language.
I think most people agree that switching languages often is very helpful for your career. It can give you new perspectives and it can add tools to your belt to solve problems that were not possible or very hard to deal with, in the languages you’ve used before that.
Another positive that I stumble upon every time is the urge to start a new pet project in the new language. Aside from doing code challenges, this is the next best option for learning languages. I always dust up my idea notes to find something that will be cool to try to start working on (actually finishing pet projects is another thing though).
more languages = more flexibility = more opportunities