Hmm as developer, I'm not sure, I actually like what I'm doing and I'm a jack of all traits. I would like to have more time to study computer science problems. Doing the math and some interesting small things like stream transformations or helping building a compiler writing libraries for different algorithms in different languages.
Things other people can use if they want. Writing big applications and help designing large scale systems is fun too even smaller pages can be fun. But i don't feel any love in the frontend I always just want to see what's possible not moving buttons or widgets around. That's why I love designers and frontend devs ... i don't want to spend hours communicate over secondary and primary colors or if a slider is better better UX in case XYZ ... I still have to do this a lot because my girlfriend does design and UX optimizations but .... I love her a lot ... customers don't have that benefit ;D ...
Anyhow I think "to learn" is the tl;dr answer :)