I'm not sure why whether I do work for free and in my spare time is a good gauge of programmer ability or that they're a desirable hire.

You wouldn't judge a mechanical engineer by whether they've built a car in their spare time, or an accountant by whether they spend their spare time doing accounting.

Some of us have lives outside of work, and like to spend our spare time away from a computer. I spend 9 hours a day in front of a computer at work, plus probably an hour outside of work doing chores. That's plenty for me. In my weekends, I like to actually get outside and do something away from a computer.

Also, depending on what you do, there's often not a lot that you could do open source. If you're an embedded systems developer for instance (like OP's wife, who is an EE), there's not a whole lot you can put up on Github.