Even when I was between jobs a couple months ago I neglected to complete a take-home interview exercise, because the opportunity cost still exists. The advantage to interviewing in person is that the conversation goes both ways. I was interviewing daily, so I still valued my spare time for personal activities.

Edit: I most likely would have completed it if I were offered some type of compensation, even below market. They claimed it was an exercise and they wouldn't use it, but this was a startup with about 10 employees, and the deliverable was definitely something they could have used. That alone rubbed me the wrong way.