The way I see it there are only a few reasons that I would ever do a side project.
1. To make more money now by freelancing.
2. To make more money in the future by learning new skills or heck at the point, just to keep up with the technology to stay employable.
3. A great idea that I think I can make money on.
4. For fun
Taking those reasons into account:
1. We make enough now to be comfortable and I'm not willing to prioritize making more money over exercising or spending time with my family and friends.
2. I try to make sure I have a job that lets me keep learning. I'll spend extra time at work trying to figure out a new to me technology to incorporate in my job. That's the quickest way to learn how something works in a real world environment.
3. I really don't have any great money making ideas.
4. I find coding and problem solving "fun" That's why I enjoy my job. If I'm not enjoying my job, it's time to get a new one.
But I do spend maybe 5-6 hours a week studying and watching tech videos in my downtime or when I'm working out in my home gym.