https://www.youtube.com/watch?v=ALy9TugTmmA
I got into it originally because when I was learning how to program, I found a bunch of tutorials, open source programs, and small games on places like Programmers Haven (which used to serve text files, source, and programs, but has since renamed to Programmers Heaven and is just a generic message board now).
Being able to type in some relatively simple code and produce a complicated-looking visual effect is highly appealing and lends to the sense of wonder. It pushes the limits of the computer and the imagination and is a gateway into learning more to see what else the computer is capable of doing.
While I never got into anything like game development from it, the demoscene has taught me that the most obvious approach might not be the only one, or even the right one for what you're trying to do. The more techniques you know, the more you can apply, and that you can often reframe a problem to hit it with another more effective technique if your current attempts aren't quite good enough.
I also created Traxer (later called Traxernews) which was a music release news website. It was my very first attempt at making a website, and it eventually led to me being a full time freelance developer.
I still plan on making music again some day, but between work, having a kid, and video games, I just don't take the time anymore.