Having been in the academia I can tell you that from my experience there's two main reasons why scientists are often reluctant to share their code:
A) embarassement at having other people see how bad it is. Not necessarily wrong, but bad in other ways.
B) wanting to keep an advantage by continuing to publish on top of the work already done, whereas anyone else wanting to get in on the same idea would have to first re-build the original work.
A) embarassement at having other people see how bad it is. Not necessarily wrong, but bad in other ways.
B) wanting to keep an advantage by continuing to publish on top of the work already done, whereas anyone else wanting to get in on the same idea would have to first re-build the original work.