I think it's just very common. When I was in high school, I built my own C compiler just to learn how things work under the hood. I'd assume that it's similar

I think it's just very common. When I was in high school, I built my own C compiler just to learn how things work under the hood. I'd assume that it's similar for others in that their programming languages aren't up to date or practically usable, but more like cool side-effects of their learning journey.