Patience, and I will get there - to explain why we are "where we are" with oil shale I thought it best to start at the beginning and gradually explain why the process has evolved to the point where it is today.  And it is way too long for a single post so there will probably be a short series of these as I go through some of the issues.

At a guess, for the same reason in-situ coal gasification is being examined.  Using a hole in the ground vs reactors saves a lot of investment.

  Ther are several reasons for attempting to develop oil shale. First, there are research and development tax credits so the research is not costing them much. Second, the major oil companies are absolutely terrified of a punative "windfall profits" tax, and they see this as great public relations for developing alternative energy sources. Third, In Situ minining leaves the waste in place so there is comparitively little remediation and environmental flack. And Fourth-it just might work and be a very economic way to produce energy.