The Cabinet Minister's job isn't to be an expert in the field of "insert department here." That is the job of Deputy Minister and other senior level civil servants who have made their careers in the field, who advises the politician running the department on all matters of the government's business for that particular scope.
Most politicians are MD's, economists and lawyers, how many fisherman do you see being elected? How many farmers? How many agrologists for that matter? How many social workers?
We don't require politicized experts...