Quantitative and qualitative data used in UX research

I am trying to find examples of user behaviour research that combines both quantitative and qualitative data. It seems to me that most of the research leans heavily or exclusively towards one approach or the other. So you often see a large-scale survey study drawing some very specific conclusions, or heat-map or eye tracking studies that make some very general conclusions. The extent to which you can interpolate or extrapolate these results surely depends on if you are able to link them to a specific context. Considering that there are obvious advantages and disadvantages to each approach, what is the major concern with researcher running studies to collect both types of information? I don't by the argument of cost or time, because if the information being collected is not accurate or cannot be put into context correctly then it is a much bigger waste of time.

One of the key take-home messages for UX practitioners from Comparative Usability Evaluation 8 is to:

"Combine qualitative and quantitative findings in your report. Present what happened and support it with why it happened."

Because by applying qualitative and quantitative research methods you are able to treat a problem by linking the symptoms (what happened) to the root cause of the problem (why it happened).

Why isn't quantitative and qualitative data collected at the same time in more UX research/studies?