Developing game engines as a hobby means that close friends, family, and most other people will never recognize the time, effort, and passion that goes into what I do. It's very exhausting to need to heavily simplify everything just to talk about what I love, which is often why I don't.
Even worse, it's not hard to just get an off-the-shelf game engine and make something that looks cooler, and make it your own. Because I'm talking about the insides: the deeply technical code stuff that nobody understands. And I'd say it's an art, even if built for just a practical purpose.
From small snippets of codes to major design decisions, these are influenced by my life experiences and are an expression of my soul and contain a personal touch.
Drawing art is far easier for others to understand, in comparison. It can be fulfilling, but I don't consider it my 'main' hobby.