I don't have time for side projects. My work consumes all of my productive time. Granted, I am a researcher, but I think this should apply to others as well.

In work I'm concerned with writing code my colleagues can maintain. Often the most sensible design decision is to use the technology stack my team mates and I already know. If everyone else uses Linux to write Python web apps I'd need a very good reason to write a Windows only GUI app in C#!

Five years from now, my employer's standard technology stack might be obsolete. If I only gain skills at work, my skill set would be obsolete too. This would harm my future career prospects.

Could an employer pay me enough that I'd give up my side projects, sabotaging my future career prospects? Probably, but it would have to be a lot of money.

Of course, I also maintain a healthy work/life balance and have hobbies that let me get away from the computer and meet other people. This is also important.

I realize that my intended meaning was weaker than my wording. I meant that surely there are others that this should apply to. That is, surely researchers are not unique. But I don't mean that it should apply to everyone.

I'm much like you. But there are enough side projects at work to keep me challenged. In fact I am working on one now. It started as an idea I had a couple of months ago and it's grown into a team. I have another skunkworks project up my sleeve once this thing is in decent enough shape...

As a researcher, your work day is your free time to do fun stuff! Similar for people who have 20% Time. The rest of us need an occasional outlet for creativity that isn't part of the narrow junk we get paid for.

Trust me, I have overhead as well. Meetings, traveling, presentations, and sometimes tasks that are necessary but not research. I consider the actual research "real work," and some weeks I can get more "real work" done than others. And certainly I have interests that I can't satisfy with the research I'm paid to do. But, there is so much interesting research to do that I am paid for, that it's just not a good use of my time to spend it on those other things. The way things are set up for me, the best time investment for interesting result return is going to be with my paid work.

That's me, though. My overall point was that surely there are developers out there who feel the same about their job, even if it's not labeled "research."